From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Samuel Attard <samuel.r.attard@gmail.com>
Date: Thu, 20 Sep 2018 17:48:49 -0700
Subject: mas: avoid private macOS API usage

* Use the stub killring file when building blink
* Remove usage of the following private APIs
  * abort_report_np
  * pthread_fchdir_np
  * pthread_chdir_np
  * SetApplicationIsDaemon
  * _LSSetApplicationLaunchServicesServerConnectionStatus
  * AreDeviceAndUserJoinedToDomain
  * _CFIsObjC
  * CGSSetWindowCaptureExcludeShape
  * CGRegionCreateWithRect
  * CTFontCopyVariationAxesInternal
  * AudioDeviceDuck
  * NSNextStepFrame
  * NSThemeFrame
  * NSTextInputReplacementRangeAttributeName
  * _toolbarView
  * _menuImpl
  * _removeFromGroups:
  * _isConsideredOpenForPersistentState
  * _boundsIfOpen
  * _resizeDirectionForMouseLocation:
  * NSAppendToKillRing
  * kCFBundleNumericVersionKey
  * __NSNewKillRingSequence
  * __NSInitializeKillRing
  * NSYankFromKillRing
  * NSSetKillRingToYankedState
* NSAccessibilityRemoteUIElement is unnecessary for Electron's use-case. We use it
for progressive web apps (where the AXTree is in the browser process, but macOS
needs to think it's coming from the PWA process). I think it can just be chopped
out -- if there are any side-effects, we should be able to work around them.
* CAContext removal
  * For apps that spend a lot of time watching video (especially fullscreen video),
    the power/battery usage will likely increase 1.5x to 2x. For something that is,
    e.g, scrolling, it'll be smaller, more like 1.15x or 1.25x.

    In terms of performance, the impact will likely be fairly small -- any app that
    could hit 60fps before will likely still be able to hit 60fps. There may even be
    cases where performance improves when disabling remote CoreAnimation (remote
    CoreAnimation is really only about battery usage).
* CTFontDescriptorIsSystemUIFont is a private API, we're using an
_interesting_ technique in the MAS build to determine if the font is a
system font by checking if it's kCTFontPriorityAttribute is set to
system priority.

diff --git a/base/BUILD.gn b/base/BUILD.gn
index d0317b2920ca8b545d3294d6121aa0085969ab0b..e0149246c75790298cb3c107752a61daa5fc96d1 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -1079,6 +1079,7 @@ component("base") {
     "//build:ios_buildflags",
     "//build/config/compiler:compiler_buildflags",
     "//third_party/modp_b64",
+    "//electron/build/config:generate_mas_config",
   ]
 
   # Used by metrics/crc32
diff --git a/base/allocator/BUILD.gn b/base/allocator/BUILD.gn
index 2cc49d83a83c6c64780da3f2caa009908a36dd7c..e2941ac5177d3ca59859482b668b716f58d6f5d4 100644
--- a/base/allocator/BUILD.gn
+++ b/base/allocator/BUILD.gn
@@ -28,6 +28,7 @@ if (is_apple) {
     deps = [
       ":buildflags",
       "//base/allocator/partition_allocator:buildflags",
+      "//electron/build/config:generate_mas_config",
     ]
   }
 }
diff --git a/base/allocator/early_zone_registration_apple.cc b/base/allocator/early_zone_registration_apple.cc
index 416e541436d201aabca26cdbf7e8477103bd014c..8c5f92b03d67e5f0587b0e94209690611e3b082a 100644
--- a/base/allocator/early_zone_registration_apple.cc
+++ b/base/allocator/early_zone_registration_apple.cc
@@ -197,15 +197,33 @@ void EarlyMallocZoneRegistration() {
   // a duplicate even when a binary copy of this code exists.
   if (allocator_shim::IsZoneAlreadyRegistered(
           allocator_shim::kDelegatingZoneName)) {
+#if !IS_MAS_BUILD()
     abort_report_np(
         "The delegating default zone has unexpectedly already been "
         "registered.");
+#else
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunsafe-buffer-usage"
+    os_log_fault(OS_LOG_DEFAULT, "The delegating default zone "
+                 "has unexpectedly already been registered.");
+#pragma clang diagnostic pop
+    abort();
+#endif
   }
   if (allocator_shim::IsZoneAlreadyRegistered(
           allocator_shim::kPartitionAllocZoneName)) {
+#if !IS_MAS_BUILD()
     abort_report_np(
         "The PartitionAlloc default zone has unexpectedly already been "
         "registered.");
+#else
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunsafe-buffer-usage"
+    os_log_fault(OS_LOG_DEFAULT, "The PartitionAlloc default zone "
+                 "has unexpectedly already been registered.");
+#pragma clang diagnostic pop
+    abort();
+#endif
   }
 
   // Register puts the new zone at the end, unregister swaps the new zone with
@@ -229,7 +247,16 @@ void EarlyMallocZoneRegistration() {
 
   // Sanity check.
   if (allocator_shim::GetDefaultMallocZoneOrDie() != &g_delegating_zone) {
+#if !IS_MAS_BUILD()
     abort_report_np("Failed to install the delegating zone as default.");
+#else
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunsafe-buffer-usage"
+    os_log_fault(OS_LOG_DEFAULT, "Failed to install the delegating zone "
+                 "as default.");
+#pragma clang diagnostic pop
+    abort();
+#endif
   }
 }
 
diff --git a/base/allocator/partition_allocator/src/partition_alloc/BUILD.gn b/base/allocator/partition_allocator/src/partition_alloc/BUILD.gn
index 8b706f07b3c370f1a6f83ac23e508a0a22eae1db..d85a8886cc1bbe65359c03dc1e3e9b014d543ecc 100644
--- a/base/allocator/partition_allocator/src/partition_alloc/BUILD.gn
+++ b/base/allocator/partition_allocator/src/partition_alloc/BUILD.gn
@@ -987,6 +987,7 @@ if (is_clang_or_gcc) {
       ":allocator_base",
       ":allocator_core",
       ":buildflags",
+      "//electron/build/config:generate_mas_config",
     ]
   }
 }  # if (is_clang_or_gcc)
diff --git a/base/allocator/partition_allocator/src/partition_alloc/shim/early_zone_registration_utils_apple.h b/base/allocator/partition_allocator/src/partition_alloc/shim/early_zone_registration_utils_apple.h
index 725b3d78c27d9621500d8193b0b4e45c6103cff0..cd3580fb4b7261b5d8e6ff691214e432c0170dc4 100644
--- a/base/allocator/partition_allocator/src/partition_alloc/shim/early_zone_registration_utils_apple.h
+++ b/base/allocator/partition_allocator/src/partition_alloc/shim/early_zone_registration_utils_apple.h
@@ -12,16 +12,21 @@
 
 #include <mach/mach.h>
 #include <malloc/malloc.h>
+#include <os/log.h>
 
 #include <span>
 #include <string_view>
 
+#include "electron/mas.h"
+
+#if !IS_MAS_BUILD()
 extern "C" {
 // abort_report_np() records the message in a special section that both the
 // system CrashReporter and Crashpad collect in crash reports. See also in
 // chrome_exe_main_mac.cc.
 void abort_report_np(const char* fmt, ...);
 }  // extern "C"
+#endif
 
 namespace allocator_shim {
 
@@ -34,7 +39,15 @@ inline std::span<malloc_zone_t*> GetMallocZonesOrDie() {
   kern_return_t result = malloc_get_all_zones(
       mach_task_self(), /*reader=*/nullptr, &zones, &zone_count);
   if (result != KERN_SUCCESS) [[unlikely]] {
+#if !IS_MAS_BUILD()
     abort_report_np("Cannot enumerate malloc zones.");
+#else
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunsafe-buffer-usage"
+    os_log_fault(OS_LOG_DEFAULT, "Cannot enumerate malloc zones.");
+#pragma clang diagnostic pop
+    abort();
+#endif
   }
   // This is not guaranteed by the C++ standard, but commonly satisfied.
   // It must be safe to assume the same memory layout for arrays of two
diff --git a/base/enterprise_util_mac.mm b/base/enterprise_util_mac.mm
index 4bf9a3c27e05c6635b2beb8e880b5b43dbed61b5..f328fbb49c45991f44a9c75325491d0873746b61 100644
--- a/base/enterprise_util_mac.mm
+++ b/base/enterprise_util_mac.mm
@@ -16,6 +16,7 @@
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
+#include "electron/mas.h"
 
 namespace base {
 
@@ -116,6 +117,14 @@ DeviceUserDomainJoinState AreDeviceAndUserJoinedToDomain() {
     DeviceUserDomainJoinState state{.device_joined = false,
                                     .user_joined = false};
 
+#if IS_MAS_BUILD()
+    return state;
+  }();
+
+  return state;
+}
+#else
+
     @autoreleasepool {
       ODSession* session = [ODSession defaultSession];
       if (session == nil) {
@@ -219,5 +228,6 @@ DeviceUserDomainJoinState AreDeviceAndUserJoinedToDomain() {
 
   return state;
 }
+#endif
 
 }  // namespace base
diff --git a/base/mac/info_plist_data.mm b/base/mac/info_plist_data.mm
index 419a051968c58ae5a761708e4d942e8975c70852..a77032dd43f5fcbe29c54b622b34607fba09d350 100644
--- a/base/mac/info_plist_data.mm
+++ b/base/mac/info_plist_data.mm
@@ -11,15 +11,19 @@
 #include "base/apple/bundle_locations.h"
 #include "base/apple/foundation_util.h"
 #include "base/containers/span.h"
+#include "electron/mas.h"
 
+#if !IS_MAS_BUILD()
 extern "C" {
 // Key used within CoreFoundation for loaded Info plists
 extern const CFStringRef _kCFBundleNumericVersionKey;
 }
+#endif
 
 namespace base::mac {
 
 std::vector<uint8_t> OuterBundleCachedInfoPlistData() {
+#if !IS_MAS_BUILD()
   // NSBundle's info dictionary is used to ensure that any changes to Info.plist
   // on disk due to pending updates do not result in a version of the data being
   // used that doesn't match the code signature of the running app.
@@ -43,6 +47,9 @@
                      error:nullptr];
   base::span<const uint8_t> span = apple::NSDataToSpan(data);
   return {span.begin(), span.end()};
+#else
+  return {};
+#endif
 }
 
 }  // namespace base::mac
diff --git a/base/process/launch_mac.cc b/base/process/launch_mac.cc
index b63d58da9837ba4d1e4aff8f24f2cd977c5ed02d..49b4c0b69731386ef5a4b7dfb782aa8f4ae09cdd 100644
--- a/base/process/launch_mac.cc
+++ b/base/process/launch_mac.cc
@@ -84,6 +84,10 @@ int posix_spawnattr_set_csm_np(const posix_spawnattr_t*, uint32_t)
 #include "base/threading/scoped_blocking_call.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/trace_event/trace_event.h"
+#include "electron/mas.h"
+#if IS_MAS_BUILD()
+#include <sys/syscall.h>
+#endif
 
 #if BUILDFLAG(IS_MAC)
 #include "base/apple/mach_port_rendezvous_mac.h"
@@ -92,9 +96,11 @@ int posix_spawnattr_set_csm_np(const posix_spawnattr_t*, uint32_t)
 extern "C" {
 // Changes the current thread's directory to a path or directory file
 // descriptor.
+#if !IS_MAS_BUILD()
 int pthread_chdir_np(const char* dir);
 
 int pthread_fchdir_np(int fd);
+#endif
 
 int responsibility_spawnattrs_setdisclaim(posix_spawnattr_t attrs,
                                           int disclaim);
@@ -171,13 +177,27 @@ class PosixSpawnFileActions {
 
 #if !BUILDFLAG(IS_MAC)
 int ChangeCurrentThreadDirectory(const char* path) {
+#if IS_MAS_BUILD()
+  #pragma clang diagnostic push
+  #pragma clang diagnostic ignored "-Wdeprecated-declarations"
+  return syscall(SYS___pthread_chdir, path);
+  #pragma clang diagnostic pop
+#else
   return pthread_chdir_np(path);
+#endif
 }
 
 // The recommended way to unset a per-thread cwd is to set a new value to an
 // invalid file descriptor, per libpthread-218.1.3/private/private.h.
 int ResetCurrentThreadDirectory() {
+#if IS_MAS_BUILD()
+  #pragma clang diagnostic push
+  #pragma clang diagnostic ignored "-Wdeprecated-declarations"
+  return syscall(SYS___pthread_fchdir, -1);
+  #pragma clang diagnostic pop
+#else
   return pthread_fchdir_np(-1);
+#endif
 }
 #endif
 
@@ -301,16 +321,16 @@ Process LaunchProcess(const std::vector<std::string>& argv,
     file_actions.Inherit(STDERR_FILENO);
   }
 
-#if BUILDFLAG(IS_MAC)
+#if !IS_MAS_BUILD()
   if (options.disclaim_responsibility) {
     DPSXCHECK(responsibility_spawnattrs_setdisclaim(attr.get(), 1));
   }
+#endif
 
   EnvironmentMap new_environment_map = options.environment;
+#if !IS_MAS_BUILD()
   MachPortRendezvousServerMac::AddFeatureStateToEnvironment(
       new_environment_map);
-#else
-  const EnvironmentMap& new_environment_map = options.environment;
 #endif
 
   std::vector<char*> argv_cstr;
diff --git a/base/process/process_info_mac.mm b/base/process/process_info_mac.mm
index e12c1d078147d956a1d9b1bc498c1b1d6fe7b974..233362259dc4e728ed37435e650417647b45a6af 100644
--- a/base/process/process_info_mac.mm
+++ b/base/process/process_info_mac.mm
@@ -4,15 +4,20 @@
 
 #include "base/process/process_info.h"
 
+#include "electron/mas.h"
+
 #import <AppKit/AppKit.h>
 #include <unistd.h>
 
+#if !IS_MAS_BUILD()
 extern "C" {
 pid_t responsibility_get_pid_responsible_for_pid(pid_t);
 }
+#endif
 
 namespace {
 
+#if !IS_MAS_BUILD()
 bool AppContainsBluetoothUsageDescription(NSRunningApplication* app) {
   NSURL* bundle_url = app.bundleURL;
   if (!bundle_url) {
@@ -24,12 +29,14 @@ bool AppContainsBluetoothUsageDescription(NSRunningApplication* app) {
       [bundle objectForInfoDictionaryKey:@"NSBluetoothAlwaysUsageDescription"];
   return bluetooth_entry != nil;
 }
+#endif
 
 }  // namespace
 
 namespace base {
 
 bool DoesResponsibleProcessHaveBluetoothMetadata() {
+#if !IS_MAS_BUILD()
   const pid_t pid = getpid();
   const pid_t responsible_pid = responsibility_get_pid_responsible_for_pid(pid);
   // Returns true directly if this is a self-responsible app(e.g. Chrome opens
@@ -46,6 +53,9 @@ bool DoesResponsibleProcessHaveBluetoothMetadata() {
     return AppContainsBluetoothUsageDescription(app);
   }
   return false;
+#else
+  return true;
+#endif
 }
 
 }  // namespace base
diff --git a/components/os_crypt/common/keychain_password_mac.mm b/components/os_crypt/common/keychain_password_mac.mm
index 66e0c5e9779959bcc45ef1f274f98a00de1c01e1..944f58043b9f634e79c9a9840a39c26966560f02 100644
--- a/components/os_crypt/common/keychain_password_mac.mm
+++ b/components/os_crypt/common/keychain_password_mac.mm
@@ -20,6 +20,7 @@
 #include "build/branding_buildflags.h"
 #include "crypto/apple/keychain.h"
 #include "crypto/apple/keychain_v2.h"
+#include "electron/mas.h"
 #include "third_party/abseil-cpp/absl/cleanup/cleanup.h"
 
 using crypto::apple::KeychainV2;
diff --git a/components/os_crypt/sync/BUILD.gn b/components/os_crypt/sync/BUILD.gn
index 57b209f51ef1629f1201e4ba5d713c0ce32ebb24..2535b697f48fb5a28ee65d3cc651db5e5bc17b24 100644
--- a/components/os_crypt/sync/BUILD.gn
+++ b/components/os_crypt/sync/BUILD.gn
@@ -60,6 +60,7 @@ component("sync") {
     deps += [
       "//components/os_crypt/common:keychain_password_mac",
       "//crypto:mock_apple_keychain",
+      "//electron/build/config:generate_mas_config"
     ]
   } else if (is_win) {
     sources += [ "os_crypt_win.cc" ]
diff --git a/components/remote_cocoa/app_shim/BUILD.gn b/components/remote_cocoa/app_shim/BUILD.gn
index 32001b02032379d6338e59a1cf5ce5619c4e1acb..f3827c60ee95b38acae103b2f3f4a94764610c3d 100644
--- a/components/remote_cocoa/app_shim/BUILD.gn
+++ b/components/remote_cocoa/app_shim/BUILD.gn
@@ -79,6 +79,7 @@ component("app_shim") {
     "//components/crash/core/common",
     "//components/remote_cocoa/common:mojo",
     "//components/system_media_controls",
+    "//electron/build/config:generate_mas_config",
     "//mojo/public/cpp/bindings",
     "//net",
     "//ui/accelerated_widget_mac",
diff --git a/components/remote_cocoa/app_shim/NSToolbar+Private.mm b/components/remote_cocoa/app_shim/NSToolbar+Private.mm
index 5c6f4c37205de6d7cfb91c837ad4586473cf2fdb..551dc7a0e71711eee9d5176a33b345b8b8b276fb 100644
--- a/components/remote_cocoa/app_shim/NSToolbar+Private.mm
+++ b/components/remote_cocoa/app_shim/NSToolbar+Private.mm
@@ -4,6 +4,9 @@
 
 #import "components/remote_cocoa/app_shim/NSToolbar+Private.h"
 
+#include "electron/mas.h"
+
+#if !IS_MAS_BUILD()
 // Access the private view that backs the toolbar.
 // TODO(http://crbug.com/40261565): Remove when FB12010731 is fixed in AppKit.
 @interface NSToolbar (ToolbarView)
@@ -18,3 +21,4 @@ - (NSView *)privateToolbarView {
                                                            : nil;
 }
 @end
+#endif
diff --git a/components/remote_cocoa/app_shim/application_bridge.mm b/components/remote_cocoa/app_shim/application_bridge.mm
index d5afd4be1ef4ac3fd1cfa7c09c667bc87b9a6b3a..4f005f2fe24ecfe1962fc64782fb7187161cbd7a 100644
--- a/components/remote_cocoa/app_shim/application_bridge.mm
+++ b/components/remote_cocoa/app_shim/application_bridge.mm
@@ -13,6 +13,7 @@
 #include "components/remote_cocoa/app_shim/native_widget_ns_window_bridge.h"
 #include "components/remote_cocoa/app_shim/native_widget_ns_window_host_helper.h"
 #include "components/system_media_controls/mac/remote_cocoa/system_media_controls_bridge.h"
+#include "electron/mas.h"
 #include "mojo/public/cpp/bindings/associated_remote.h"
 #include "mojo/public/cpp/bindings/self_owned_receiver.h"
 #include "ui/accelerated_widget_mac/window_resize_helper_mac.h"
@@ -54,6 +55,7 @@
 
   // NativeWidgetNSWindowHostHelper:
   id GetNativeViewAccessible() override {
+#if !IS_MAS_BUILD()
     if (!remote_accessibility_element_) {
       base::ProcessId browser_pid = base::kNullProcessId;
       std::vector<uint8_t> element_token;
@@ -64,6 +66,9 @@ id GetNativeViewAccessible() override {
           ui::RemoteAccessibility::GetRemoteElementFromToken(element_token);
     }
     return remote_accessibility_element_;
+#else
+    return nil;
+#endif
   }
   void DispatchKeyEvent(ui::KeyEvent* event) override {
     bool event_handled = false;
@@ -102,7 +107,9 @@ void GetWordAt(const gfx::Point& location_in_content,
   mojo::AssociatedRemote<mojom::TextInputHost> text_input_host_remote_;
 
   std::unique_ptr<NativeWidgetNSWindowBridge> bridge_;
+#if !IS_MAS_BUILD()
   NSAccessibilityRemoteUIElement* __strong remote_accessibility_element_;
+#endif
 };
 
 bool g_is_out_of_process_app_shim = false;
diff --git a/components/remote_cocoa/app_shim/browser_native_widget_window_mac.mm b/components/remote_cocoa/app_shim/browser_native_widget_window_mac.mm
index f7200edbe6059ac6d7ade0672852b52da7642a71..0cc5da96411b46eb39d0c01dfec59cb503df0d9b 100644
--- a/components/remote_cocoa/app_shim/browser_native_widget_window_mac.mm
+++ b/components/remote_cocoa/app_shim/browser_native_widget_window_mac.mm
@@ -9,7 +9,9 @@
 #include "base/mac/mac_util.h"
 #include "components/remote_cocoa/app_shim/native_widget_ns_window_bridge.h"
 #include "components/remote_cocoa/common/native_widget_ns_window_host.mojom.h"
+#include "electron/mas.h"
 
+#if !IS_MAS_BUILD()
 namespace {
 // Workaround for https://crbug.com/1369643
 const double kThinControllerHeight = 0.5;
@@ -125,12 +127,15 @@ - (void)maybeShowTrafficLights {
 
 @end
 
+#endif  // MAS_BUILD
+
 @implementation BrowserNativeWidgetWindow
 
 @synthesize thinTitlebarViewController = _thinTitlebarViewController;
 
 // NSWindow (PrivateAPI) overrides.
 
+#if !IS_MAS_BUILD()
 + (Class)frameViewClassForStyleMask:(NSUInteger)windowStyle {
   // - NSThemeFrame and its subclasses will be nil if it's missing at runtime.
   if ([BrowserWindowFrame class])
@@ -189,6 +194,8 @@ - (BOOL)_usesCustomDrawing {
   return NO;
 }
 
+#endif  // MAS_BUILD
+
 // Handle "Move focus to the window toolbar" configured in System Preferences ->
 // Keyboard -> Shortcuts -> Keyboard. Usually Ctrl+F5. The argument (|unknown|)
 // tends to just be nil.
@@ -199,8 +206,8 @@ - (void)_handleFocusToolbarHotKey:(id)unknown {
 }
 
 - (void)setAlwaysShowTrafficLights:(BOOL)alwaysShow {
-  [base::apple::ObjCCastStrict<BrowserWindowFrame>(self.contentView.superview)
-      setAlwaysShowTrafficLights:alwaysShow];
+  // [base::apple::ObjCCastStrict<BrowserWindowFrame>(self.contentView.superview)
+  //    setAlwaysShowTrafficLights:alwaysShow];
 }
 
 @end
diff --git a/components/remote_cocoa/app_shim/menu_controller_cocoa_delegate_impl.mm b/components/remote_cocoa/app_shim/menu_controller_cocoa_delegate_impl.mm
index 5dd3ae5dff160834524c013594f76f59ad7e2fdd..356d677b9e6addeeb60af6b4e2d63125bc4f51c4 100644
--- a/components/remote_cocoa/app_shim/menu_controller_cocoa_delegate_impl.mm
+++ b/components/remote_cocoa/app_shim/menu_controller_cocoa_delegate_impl.mm
@@ -8,6 +8,7 @@
 #include "base/apple/foundation_util.h"
 #include "base/logging.h"
 #import "base/message_loop/message_pump_apple.h"
+#import "electron/mas.h"
 #import "skia/ext/skia_utils_mac.h"
 #import "ui/base/cocoa/cocoa_base_utils.h"
 #include "ui/base/interaction/element_tracker_mac.h"
@@ -111,6 +112,7 @@ - (void)highlightItemAtIndex:(NSInteger)index;
 
 @interface NSMenu (Impl)
 
+#if !IS_MAS_BUILD()
 // Returns the impl. (If called on macOS 14 this would return a subclass of
 // NSCocoaMenuImpl, but private API use is not needed on macOS 14.)
 - (id<CrNSCarbonMenuImpl>)_menuImpl;
@@ -119,6 +121,7 @@ @interface NSMenu (Impl)
 // on both Carbon and Cocoa impls, but always (incorrectly) returns a zero
 // origin with the Cocoa impl. Therefore, do not use with macOS 14 or later.
 - (CGRect)_boundsIfOpen;
+#endif
 
 @end
 
@@ -239,6 +242,7 @@ - (void)controllerWillAddMenu:(NSMenu*)menu fromModel:(ui::MenuModel*)model {
       }
       menuShown = true;
 
+#if !IS_MAS_BUILD()
       if (alertedIndex.has_value()) {
         const auto index = base::checked_cast<NSInteger>(alertedIndex.value());
         if (@available(macOS 14.0, *)) {
@@ -247,6 +251,7 @@ - (void)controllerWillAddMenu:(NSMenu*)menu fromModel:(ui::MenuModel*)model {
           [strongMenu._menuImpl highlightItemAtIndex:index];
         }
       }
+#endif
 
       if (@available(macOS 14.0, *)) {
         for (auto [elementId, index] : elementIds) {
@@ -267,7 +272,11 @@ - (void)controllerWillAddMenu:(NSMenu*)menu fromModel:(ui::MenuModel*)model {
             dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_MSEC),
             dispatch_get_main_queue(), ^{
               gfx::Rect bounds =
+#if !IS_MAS_BUILD()
                   gfx::ScreenRectFromNSRect(strongMenu._boundsIfOpen);
+#else
+                  gfx::ScreenRectFromNSRect(NSMakeRect(0, 0, 0, 0));
+#endif
               for (auto [elementId, index] : elementIds) {
                 ui::ElementTrackerMac::GetInstance()->NotifyMenuItemShown(
                     strongMenu, elementId, bounds);
diff --git a/components/remote_cocoa/app_shim/native_widget_mac_frameless_nswindow.mm b/components/remote_cocoa/app_shim/native_widget_mac_frameless_nswindow.mm
index 3a815ebf505bd95fa7f6b61ba433d98fbfe20225..149de0175c2ec0e41e3ba40caad7019ca87386d6 100644
--- a/components/remote_cocoa/app_shim/native_widget_mac_frameless_nswindow.mm
+++ b/components/remote_cocoa/app_shim/native_widget_mac_frameless_nswindow.mm
@@ -4,6 +4,10 @@
 
 #import "components/remote_cocoa/app_shim/native_widget_mac_frameless_nswindow.h"
 
+#include "electron/mas.h"
+
+#if !IS_MAS_BUILD()
+
 @interface NSWindow (PrivateAPI)
 + (Class)frameViewClassForStyleMask:(NSUInteger)windowStyle;
 @end
@@ -18,8 +22,12 @@ - (CGFloat)_titlebarHeight {
 }
 @end
 
+#endif  // MAS_BUILD
+
 @implementation NativeWidgetMacFramelessNSWindow
 
+#if !IS_MAS_BUILD()
+
 + (Class)frameViewClassForStyleMask:(NSUInteger)windowStyle {
   if ([NativeWidgetMacFramelessNSWindowFrame class]) {
     return [NativeWidgetMacFramelessNSWindowFrame class];
@@ -27,4 +35,6 @@ + (Class)frameViewClassForStyleMask:(NSUInteger)windowStyle {
   return [super frameViewClassForStyleMask:windowStyle];
 }
 
+#endif  // MAS_BUILD
+
 @end
diff --git a/components/remote_cocoa/app_shim/native_widget_mac_nswindow.h b/components/remote_cocoa/app_shim/native_widget_mac_nswindow.h
index 48f47bf3eeb8464d1c3925f0f73f62c790cac2f0..b7b2b7c1b7e99927012ce1676cc753b2bcdd887b 100644
--- a/components/remote_cocoa/app_shim/native_widget_mac_nswindow.h
+++ b/components/remote_cocoa/app_shim/native_widget_mac_nswindow.h
@@ -10,6 +10,7 @@
 #include "base/apple/foundation_util.h"
 #import "components/remote_cocoa/app_shim/native_widget_mac_nswindow_headless.h"
 #include "components/remote_cocoa/app_shim/remote_cocoa_app_shim_export.h"
+#include "electron/mas.h"
 #import "ui/base/cocoa/command_dispatcher.h"
 
 namespace remote_cocoa {
@@ -18,6 +19,7 @@ class NativeWidgetNSWindowBridge;
 
 @protocol WindowTouchBarDelegate;
 
+#if !IS_MAS_BUILD()
 // Weak lets Chrome launch even if a future macOS doesn't have the below classes
 WEAK_IMPORT_ATTRIBUTE
 @interface NSNextStepFrame : NSView
@@ -34,6 +36,7 @@ REMOTE_COCOA_APP_SHIM_EXPORT
 REMOTE_COCOA_APP_SHIM_EXPORT
 @interface NativeWidgetMacNSWindowTitledFrame : NSThemeFrame
 @end
+#endif
 
 // The NSWindow used by BridgedNativeWidget. Provides hooks into AppKit that
 // can only be accomplished by overriding methods.
diff --git a/components/remote_cocoa/app_shim/native_widget_mac_nswindow.mm b/components/remote_cocoa/app_shim/native_widget_mac_nswindow.mm
index a5fc9193711a7cc2eee45171178c070321177ca2..94bd32ce1ddd3f8b4315cd06be59d7550b591891 100644
--- a/components/remote_cocoa/app_shim/native_widget_mac_nswindow.mm
+++ b/components/remote_cocoa/app_shim/native_widget_mac_nswindow.mm
@@ -22,6 +22,7 @@
 #import "components/remote_cocoa/app_shim/views_nswindow_delegate.h"
 #import "components/remote_cocoa/app_shim/window_touch_bar_delegate.h"
 #include "components/remote_cocoa/common/native_widget_ns_window_host.mojom.h"
+#include "electron/mas.h"
 #include "ui/accessibility/platform/ax_platform_node.h"
 #import "ui/base/cocoa/user_interface_item_command_handler.h"
 #import "ui/base/cocoa/window_size_constants.h"
@@ -109,20 +110,24 @@ void OrderChildWindow(NSWindow* child_window,
 
 }  // namespace
 
+#if !IS_MAS_BUILD()
 @interface NSNextStepFrame (Private)
 - (instancetype)initWithFrame:(NSRect)frame
                     styleMask:(NSUInteger)styleMask
                         owner:(id)owner;
 @end
+#endif
 
 @interface NSWindow (Private)
+#if !IS_MAS_BUILD()
 + (Class)frameViewClassForStyleMask:(NSWindowStyleMask)windowStyle;
-- (BOOL)hasKeyAppearance;
 - (long long)_resizeDirectionForMouseLocation:(CGPoint)location;
 - (BOOL)_isConsideredOpenForPersistentState;
 - (void)_zoomToScreenEdge:(NSUInteger)edge;
 - (void)_removeFromGroups:(NSWindow*)window;
 - (BOOL)_isNonactivatingPanel;
+#endif
+- (BOOL)hasKeyAppearance;
 @end
 
 struct NSEdgeAndCornerThicknesses {
@@ -159,13 +164,30 @@ - (void)cr_mouseDownOnFrameView:(NSEvent*)event;
 @implementation NSView (CRFrameViewAdditions)
 // If a mouseDown: falls through to the frame view, turn it into a window drag.
 - (void)cr_mouseDownOnFrameView:(NSEvent*)event {
+#if !IS_MAS_BUILD()
   if ([self.window _resizeDirectionForMouseLocation:event.locationInWindow] !=
       -1)
     return;
+#else
+  // For MAS builds, approximate the resize direction check.
+  if (self.window.styleMask & NSWindowStyleMaskResizable) {
+    constexpr CGFloat kResizeThreshold = 5.0;
+    NSPoint location = event.locationInWindow;
+    NSRect frame = self.window.frame;
+    CGFloat width = NSWidth(frame);
+    CGFloat height = NSHeight(frame);
+    if (location.x < kResizeThreshold || location.x > width - kResizeThreshold ||
+        location.y < kResizeThreshold || location.y > height - kResizeThreshold) {
+      return;
+    }
+  }
+#endif
   [self.window performWindowDragWithEvent:event];
 }
 @end
 
+#if !IS_MAS_BUILD()
+
 @implementation NativeWidgetMacNSWindowTitledFrame
 - (void)mouseDown:(NSEvent*)event {
   if (self.window.isMovable)
@@ -193,6 +215,8 @@ - (BOOL)usesCustomDrawing {
 }
 @end
 
+#endif  // MAS_BUILD
+
 @implementation NativeWidgetMacNSWindow {
  @private
   CommandDispatcher* __strong _commandDispatcher;
@@ -268,6 +292,7 @@ - (BOOL)invokeOriginalIsVisibleForTesting {
 // bubbles and the find bar, but these should not be movable.
 // Instead, let's push this up to the parent window which should be
 // the browser.
+#if !IS_MAS_BUILD()
 - (void)_zoomToScreenEdge:(NSUInteger)edge {
   if (self.parentWindow) {
     [self.parentWindow _zoomToScreenEdge:edge];
@@ -275,6 +300,7 @@ - (void)_zoomToScreenEdge:(NSUInteger)edge {
     [super _zoomToScreenEdge:edge];
   }
 }
+#endif
 
 // This override helps diagnose lifetime issues in crash stacktraces by
 // inserting a symbol on NativeWidgetMacNSWindow and should be kept even if it
@@ -407,6 +433,8 @@ - (NSAccessibilityRole)accessibilityRole {
 
 // NSWindow overrides.
 
+#if !IS_MAS_BUILD()
+
 + (Class)frameViewClassForStyleMask:(NSWindowStyleMask)windowStyle {
   if (windowStyle & NSWindowStyleMaskTitled) {
     if (Class customFrame = [NativeWidgetMacNSWindowTitledFrame class])
@@ -418,6 +446,8 @@ + (Class)frameViewClassForStyleMask:(NSWindowStyleMask)windowStyle {
   return [super frameViewClassForStyleMask:windowStyle];
 }
 
+#endif
+
 - (NSRect)constrainFrameRect:(NSRect)frameRect toScreen:(NSScreen*)screen {
   if (self.isHeadless || self.parentWindow) {
     // AppKit's default implementation moves child windows down to avoid
@@ -455,12 +485,14 @@ - (BOOL)_usesCustomDrawing {
 // if it were valid to set that style for windows, setting the window style
 // recalculates and re-caches a bunch of stuff, so a surgical override is the
 // cleanest approach.
+#if !IS_MAS_BUILD()
 - (BOOL)_isNonactivatingPanel {
   if (_activationIndependence) {
     return YES;
   }
   return [super _isNonactivatingPanel];
 }
+#endif
 
 + (void)_getExteriorResizeEdgeThicknesses:
             (NSEdgeAndCornerThicknesses*)outThicknesses
@@ -714,9 +746,11 @@ - (id)archiver:(NSKeyedArchiver*)archiver willEncodeObject:(id)object {
 }
 
 - (void)saveRestorableState {
+#if !IS_MAS_BUILD()
   if (!_bridge || ![self _isConsideredOpenForPersistentState]) {
     return;
   }
+#endif
 
   // Certain conditions, such as in the Speedometer 3 benchmark, can trigger a
   // rapid succession of calls to saveRestorableState. If there's no pending
@@ -783,6 +817,7 @@ - (void)reallySaveRestorableState {
 // affects its restorable state changes.
 - (void)invalidateRestorableState {
   [super invalidateRestorableState];
+#if !IS_MAS_BUILD()
   if ([self _isConsideredOpenForPersistentState]) {
     if (_willUpdateRestorableState)
       return;
@@ -795,6 +830,7 @@ - (void)invalidateRestorableState {
     _willUpdateRestorableState = NO;
     [NSObject cancelPreviousPerformRequestsWithTarget:self];
   }
+#endif
 }
 
 // On newer SDKs, _canMiniaturize respects NSWindowStyleMaskMiniaturizable in
@@ -971,6 +1007,7 @@ - (void)maybeRemoveTreeFromOrderingGroups {
   // Since _removeFromGroups: is not documented it could go away in newer
   // versions of macOS. If the selector does not exist, DumpWithoutCrashing() so
   // we hear about the change.
+#if !IS_MAS_BUILD()
   if (![NSWindow instancesRespondToSelector:@selector(_removeFromGroups:)]) {
     base::debug::DumpWithoutCrashing();
     return;
@@ -988,6 +1025,7 @@ - (void)maybeRemoveTreeFromOrderingGroups {
       [currentWindow _removeFromGroups:child];
     }
   }
+#endif
 }
 
 - (NSWindow*)rootWindow {
diff --git a/components/remote_cocoa/app_shim/native_widget_ns_window_bridge.mm b/components/remote_cocoa/app_shim/native_widget_ns_window_bridge.mm
index b89085a51a1692ddbc62e8e4b85d358bbf85533f..4d81f8bce7febc78bb620a46683f9c7dcf459227 100644
--- a/components/remote_cocoa/app_shim/native_widget_ns_window_bridge.mm
+++ b/components/remote_cocoa/app_shim/native_widget_ns_window_bridge.mm
@@ -42,6 +42,7 @@
 #import "components/remote_cocoa/app_shim/views_nswindow_delegate.h"
 #import "components/remote_cocoa/app_shim/window_move_loop.h"
 #include "components/remote_cocoa/common/native_widget_ns_window_host.mojom.h"
+#include "electron/mas.h"
 #include "mojo/public/cpp/bindings/self_owned_receiver.h"
 #include "net/cert/x509_util_apple.h"
 #include "ui/accelerated_widget_mac/window_resize_helper_mac.h"
@@ -75,10 +76,13 @@
 using CGRegionRef = CFTypeRef;
 
 CG_EXTERN CGSConnectionID CGSMainConnectionID(void);
+
+#if !IS_MAS_BUILD()
 CG_EXTERN CGError CGSSetWindowCaptureExcludeShape(CGSConnectionID cid,
                                                   CGSWindowID wid,
                                                   CGRegionRef region);
 CG_EXTERN CGRegionRef CGRegionCreateWithRect(CGRect rect);
+#endif
 
 namespace {
 constexpr auto kUIPaintTimeout = base::Milliseconds(500);
@@ -731,10 +735,12 @@ NSUInteger CountBridgedWindows(NSArray* child_windows) {
   // this should be treated as an error and caught early.
   CHECK(bridged_view_);
 
+#if !IS_MAS_BUILD()
   // Send the accessibility tokens for the NSView now that it exists.
   host_->SetRemoteAccessibilityTokens(
       ui::RemoteAccessibility::GetTokenForLocalElement(window_),
       ui::RemoteAccessibility::GetTokenForLocalElement(bridged_view_));
+#endif
 
   // Beware: This view was briefly removed (in favor of a bare CALayer) in
   // https://crrev.com/c/1236675. The ordering of unassociated layers relative
@@ -1186,6 +1192,7 @@ NSUInteger CountBridgedWindows(NSArray* child_windows) {
 }
 
 void NativeWidgetNSWindowBridge::SetAllowScreenshots(bool allow) {
+#if !IS_MAS_BUILD()
   CGSConnectionID connection_id = CGSMainConnectionID();
   CGSWindowID window_id = ns_window().windowNumber;
   CGRect frame = ns_window().frame;
@@ -1195,6 +1202,10 @@ NSUInteger CountBridgedWindows(NSArray* child_windows) {
     region.reset(CGRegionCreateWithRect(frame));
   }
   CGSSetWindowCaptureExcludeShape(connection_id, window_id, region.get());
+#else
+  [ns_window()
+        setSharingType:allow ? NSWindowSharingReadOnly : NSWindowSharingNone];
+#endif
 }
 
 void NativeWidgetNSWindowBridge::SetColorMode(
diff --git a/components/viz/service/BUILD.gn b/components/viz/service/BUILD.gn
index 10497f25d8386ae2807d0a3389ba303f75ae1b20..6ed74ce305052e3f88727d15277aa86eafdffcd0 100644
--- a/components/viz/service/BUILD.gn
+++ b/components/viz/service/BUILD.gn
@@ -390,6 +390,7 @@ viz_component("service") {
         "frame_sinks/external_begin_frame_source_mojo_mac.h",
       ]
     }
+    deps += ["//electron/build/config:generate_mas_config"]
   }
 
   if (is_ios) {
@@ -716,6 +717,7 @@ viz_source_set("unit_tests") {
       "display_embedder/software_output_device_mac_unittest.mm",
     ]
     frameworks = [ "IOSurface.framework" ]
+    deps += ["//electron/build/config:generate_mas_config"]
   }
 
   if (is_win) {
diff --git a/content/app_shim_remote_cocoa/ns_view_bridge_factory_impl.mm b/content/app_shim_remote_cocoa/ns_view_bridge_factory_impl.mm
index 010c713090e5038dc90db131c8f621422d30c03b..20c35e887a0496ee609c077e3b0494bdded41dba 100644
--- a/content/app_shim_remote_cocoa/ns_view_bridge_factory_impl.mm
+++ b/content/app_shim_remote_cocoa/ns_view_bridge_factory_impl.mm
@@ -15,6 +15,7 @@
 #include "content/common/web_contents_ns_view_bridge.mojom.h"
 #include "content/public/browser/remote_cocoa.h"
 #include "content/public/browser/render_widget_host_view_mac_delegate.h"
+#include "electron/mas.h"
 #include "mojo/public/cpp/bindings/associated_receiver.h"
 #include "mojo/public/cpp/bindings/associated_remote.h"
 #include "mojo/public/cpp/bindings/pending_associated_receiver.h"
@@ -63,7 +64,9 @@ explicit RenderWidgetHostNSViewBridgeOwner(
       const RenderWidgetHostNSViewBridgeOwner&) = delete;
 
  private:
+#if !IS_MAS_BUILD()
   NSAccessibilityRemoteUIElement* __strong remote_accessibility_element_;
+#endif
   void OnMojoDisconnect() { delete this; }
 
   std::unique_ptr<blink::WebCoalescedInputEvent> TranslateEvent(
@@ -75,6 +78,7 @@ explicit RenderWidgetHostNSViewBridgeOwner(
   }
 
   id GetAccessibilityElement() override {
+#if !IS_MAS_BUILD()
     if (!remote_accessibility_element_) {
       base::ProcessId browser_pid = base::kNullProcessId;
       std::vector<uint8_t> element_token;
@@ -85,6 +89,9 @@ id GetAccessibilityElement() override {
           ui::RemoteAccessibility::GetRemoteElementFromToken(element_token);
     }
     return remote_accessibility_element_;
+#else
+    return nil;
+#endif
   }
 
   // RenderWidgetHostNSViewHostHelper implementation.
@@ -103,8 +110,10 @@ id GetFocusedBrowserAccessibilityElement() override {
     return [bridgedContentView accessibilityFocusedUIElement];
   }
   void SetAccessibilityWindow(NSWindow* window) override {
+#if !IS_MAS_BUILD()
     host_->SetRemoteAccessibilityWindowToken(
         ui::RemoteAccessibility::GetTokenForLocalElement(window));
+#endif
   }
 
   void ForwardKeyboardEvent(const input::NativeWebKeyboardEvent& key_event,
diff --git a/content/app_shim_remote_cocoa/render_widget_host_view_cocoa.mm b/content/app_shim_remote_cocoa/render_widget_host_view_cocoa.mm
index 712d59e1f7d9681c122e6d05a8b65bccbfacb492..de24209bbd3cd4a530c6f32990a0f93a182abfc0 100644
--- a/content/app_shim_remote_cocoa/render_widget_host_view_cocoa.mm
+++ b/content/app_shim_remote_cocoa/render_widget_host_view_cocoa.mm
@@ -33,6 +33,7 @@
 #import "content/public/browser/render_widget_host_view_mac_delegate.h"
 #include "content/public/browser/scoped_accessibility_mode.h"
 #include "content/public/common/content_features.h"
+#include "electron/mas.h"
 #include "skia/ext/skia_utils_mac.h"
 #include "third_party/blink/public/common/features.h"
 #include "third_party/blink/public/mojom/input/input_handler.mojom.h"
@@ -2180,15 +2181,21 @@ - (NSAccessibilityRole)accessibilityRole {
 // Since this implementation doesn't have to wait any IPC calls, this doesn't
 // make any key-typing jank. --hbono 7/23/09
 //
+#if !IS_MAS_BUILD()
 extern "C" {
 extern NSString* NSTextInputReplacementRangeAttributeName;
 }
+#endif
 
 - (NSArray*)validAttributesForMarkedText {
   // This code is just copied from WebKit except renaming variables.
   static NSArray* const kAttributes = @[
     NSUnderlineStyleAttributeName, NSUnderlineColorAttributeName,
+#if !IS_MAS_BUILD()
     NSMarkedClauseSegmentAttributeName, NSTextInputReplacementRangeAttributeName
+#else
+    NSMarkedClauseSegmentAttributeName
+#endif
   ];
   return kAttributes;
 }
diff --git a/content/browser/BUILD.gn b/content/browser/BUILD.gn
index 2f57856179bffdc35ca14cc7b1419bee9d7bbf8e..e2f3ce4ee3cbbb3c10110981a4bccd12c9b2400c 100644
--- a/content/browser/BUILD.gn
+++ b/content/browser/BUILD.gn
@@ -344,6 +344,7 @@ source_set("browser") {
     "//ui/webui/resources",
     "//v8",
     "//v8:v8_version",
+    "//electron/build/config:generate_mas_config",
   ]
 
   public_deps = [
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.h b/content/browser/renderer_host/render_widget_host_view_mac.h
index 367834e678f44d6e71c4218d293e11c3569daf2b..c97fb8f0411b45c1a01e4fab8dc40cc3778d1d09 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.h
+++ b/content/browser/renderer_host/render_widget_host_view_mac.h
@@ -24,6 +24,7 @@
 #include "content/browser/renderer_host/text_input_manager.h"
 #include "content/common/content_export.h"
 #include "content/common/render_widget_host_ns_view.mojom.h"
+#include "electron/mas.h"
 #include "mojo/public/cpp/bindings/associated_receiver.h"
 #include "mojo/public/cpp/bindings/associated_remote.h"
 #include "third_party/blink/public/mojom/webshare/webshare.mojom.h"
@@ -54,7 +55,9 @@ class CursorManager;
 
 @protocol RenderWidgetHostViewMacDelegate;
 
+#if !IS_MAS_BUILD()
 @class NSAccessibilityRemoteUIElement;
+#endif
 @class RenderWidgetHostViewCocoa;
 
 namespace content {
@@ -679,9 +682,11 @@ class CONTENT_EXPORT RenderWidgetHostViewMac
   // EnsureSurfaceSynchronizedForWebTest().
   uint32_t latest_capture_sequence_number_ = 0u;
 
+#if !IS_MAS_BUILD()
   // Remote accessibility objects corresponding to the NSWindow that this is
   // displayed to the user in.
   NSAccessibilityRemoteUIElement* __strong remote_window_accessible_;
+#endif
 
   // Used to force the NSApplication's focused accessibility element to be the
   // content::BrowserAccessibilityCocoa accessibility tree when the NSView for
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index cf8652cb6ddbf07e114d576c192bcda99dc78e3a..c4ada35c3ca32ce06ffc57577af7bc4c45c98579 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -52,6 +52,7 @@
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/page_visibility_state.h"
+#include "electron/mas.h"
 #include "media/base/media_switches.h"
 #include "skia/ext/platform_canvas.h"
 #include "skia/ext/skia_utils_mac.h"
@@ -274,8 +275,10 @@
 void RenderWidgetHostViewMac::MigrateNSViewBridge(
     remote_cocoa::mojom::Application* remote_cocoa_application,
     uint64_t parent_ns_view_id) {
+#if !IS_MAS_BUILD()
   // Destroy the previous remote accessibility element.
   remote_window_accessible_ = nil;
+#endif
 
   // Reset `ns_view_` before resetting `remote_ns_view_` to avoid dangling
   // pointers. `ns_view_` gets reinitialized later in this method.
@@ -1687,10 +1690,12 @@ void CombineTextNodesAndMakeCallback(SpeechCallback callback,
 
 gfx::NativeViewAccessible
 RenderWidgetHostViewMac::AccessibilityGetNativeViewAccessibleForWindow() {
+#if !IS_MAS_BUILD()
   if (remote_window_accessible_) {
     return gfx::NativeViewAccessible(
         (id<NSAccessibility>)remote_window_accessible_);
   }
+#endif
   return gfx::NativeViewAccessible([GetInProcessNSView() window]);
 }
 
@@ -1742,9 +1747,11 @@ void CombineTextNodesAndMakeCallback(SpeechCallback callback,
 }
 
 void RenderWidgetHostViewMac::SetAccessibilityWindow(NSWindow* window) {
+#if !IS_MAS_BUILD()
   // When running in-process, just use the NSView's NSWindow as its own
   // accessibility element.
   remote_window_accessible_ = nil;
+#endif
 }
 
 bool RenderWidgetHostViewMac::SyncIsWidgetForMainFrame(
@@ -2269,20 +2276,26 @@ void CombineTextNodesAndMakeCallback(SpeechCallback callback,
 void RenderWidgetHostViewMac::GetRenderWidgetAccessibilityToken(
     GetRenderWidgetAccessibilityTokenCallback callback) {
   base::ProcessId pid = getpid();
+#if !IS_MAS_BUILD()
   id element_id = GetNativeViewAccessible().Get();
   std::vector<uint8_t> token =
       ui::RemoteAccessibility::GetTokenForLocalElement(element_id);
   std::move(callback).Run(pid, token);
+#else
+  std::move(callback).Run(pid, std::vector<uint8_t>());
+#endif
 }
 
 void RenderWidgetHostViewMac::SetRemoteAccessibilityWindowToken(
     const std::vector<uint8_t>& window_token) {
+#if !IS_MAS_BUILD()
   if (window_token.empty()) {
     remote_window_accessible_ = nil;
   } else {
     remote_window_accessible_ =
         ui::RemoteAccessibility::GetRemoteElementFromToken(window_token);
   }
+#endif
 }
 
 ///////////////////////////////////////////////////////////////////////////////
diff --git a/content/common/BUILD.gn b/content/common/BUILD.gn
index 20b61c2dfc3433f02f5c6b8f25386b8a9a6011db..3d88ae364383bd9721eb9c9fc4fdd6e85a20f448 100644
--- a/content/common/BUILD.gn
+++ b/content/common/BUILD.gn
@@ -271,6 +271,7 @@ source_set("common") {
     "//ui/shell_dialogs",
     "//url",
     "//url/ipc:url_ipc",
+    "//electron/build/config:generate_mas_config",
   ]
 
   defines = []
diff --git a/content/renderer/BUILD.gn b/content/renderer/BUILD.gn
index 8445214b66242eb53b2546a16078cc3d26cbdb99..8751ca6aba9caecec4d65f0059fb1b632c74ec61 100644
--- a/content/renderer/BUILD.gn
+++ b/content/renderer/BUILD.gn
@@ -324,6 +324,7 @@ target(link_target_type, "renderer") {
     "//ui/strings:auto_image_annotation_strings_grit",
     "//url",
     "//v8",
+    "//electron/build/config:generate_mas_config",
   ]
   allow_circular_includes_from = []
 
diff --git a/content/renderer/renderer_main_platform_delegate_mac.mm b/content/renderer/renderer_main_platform_delegate_mac.mm
index d4db3b179725cb96bcbd0f73db7d52ef8b7522db..703b0f56a61abac51961bfd918b7349b943900de 100644
--- a/content/renderer/renderer_main_platform_delegate_mac.mm
+++ b/content/renderer/renderer_main_platform_delegate_mac.mm
@@ -7,12 +7,15 @@
 #import <Cocoa/Cocoa.h>
 
 #include "base/check_op.h"
+#include "electron/mas.h"
 #include "sandbox/mac/seatbelt.h"
 #include "sandbox/mac/system_services.h"
 
+#if !IS_MAS_BUILD()
 extern "C" {
 CGError CGSSetDenyWindowServerConnections(bool);
 }
+#endif
 
 namespace content {
 
@@ -22,6 +25,7 @@
 // verifies there are no existing open connections), and then indicates that
 // Chrome should continue execution without access to launchservicesd.
 void DisableSystemServices() {
+#if !IS_MAS_BUILD()
   // Tell the WindowServer that we don't want to make any future connections.
   // This will return Success as long as there are no open connections, which
   // is what we want.
@@ -30,6 +34,7 @@ void DisableSystemServices() {
 
   sandbox::DisableLaunchServices();
   sandbox::DisableCoreServicesCheckFix();
+#endif
 }
 
 }  // namespace
diff --git a/content/renderer/theme_helper_mac.mm b/content/renderer/theme_helper_mac.mm
index a1068589ad844518038ee7bc15a3de9bc5cba525..1ff781c49f086ec8015c7d3c44567dbec3d00ff8 100644
--- a/content/renderer/theme_helper_mac.mm
+++ b/content/renderer/theme_helper_mac.mm
@@ -7,16 +7,28 @@
 #include <Cocoa/Cocoa.h>
 
 #include "base/strings/sys_string_conversions.h"
+#include "electron/mas.h"
 
+#if !IS_MAS_BUILD()
 extern "C" {
 bool CGFontRenderingGetFontSmoothingDisabled(void);
 }
-
+#endif
 namespace content {
 
 bool IsSubpixelAntialiasingAvailable() {
+#if !IS_MAS_BUILD()
   // See https://trac.webkit.org/changeset/239306/webkit for more info.
   return !CGFontRenderingGetFontSmoothingDisabled();
+#else
+  NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
+  NSString *default_key = @"CGFontRenderingGetFontSmoothingDisabled";
+  // Check that key exists since boolForKey defaults to NO when the
+  // key is missing and this key in fact defaults to YES;
+  if ([defaults objectForKey:default_key] == nil)
+    return false;
+  return ![defaults boolForKey:default_key];
+#endif
 }
 
 }  // namespace content
diff --git a/content/test/BUILD.gn b/content/test/BUILD.gn
index d368b2481156bb79c6e74c8b09a828eb2fa2d44c..07cbf495717714d71d977a8820e08050c3062526 100644
--- a/content/test/BUILD.gn
+++ b/content/test/BUILD.gn
@@ -700,6 +700,7 @@ static_library("test_support") {
     "//url",
     "//url/mojom:url_mojom_gurl",
     "//v8",
+    "//electron/build/config:generate_mas_config"
   ]
 
   data_deps = [
@@ -1175,6 +1176,8 @@ static_library("browsertest_support") {
   # TODO(crbug.com/40031409): Fix code that adds exit-time destructors and
   # enable the diagnostic by removing this line.
   configs += [ "//build/config/compiler:no_exit_time_destructors" ]
+
+  deps += ["//electron/build/config:generate_mas_config"]
 }
 
 mojom("content_test_mojo_bindings") {
@@ -2064,6 +2067,7 @@ test("content_browsertests") {
     "//ui/shell_dialogs",
     "//ui/snapshot",
     "//ui/webui:test_support",
+    "//electron/build/config:generate_mas_config"
   ]
 
   if (!(is_chromeos && target_cpu == "arm64" && current_cpu == "arm")) {
@@ -3412,6 +3416,7 @@ test("content_unittests") {
     "//ui/shell_dialogs",
     "//ui/webui:test_support",
     "//url",
+    "//electron/build/config:generate_mas_config",
   ]
 
   if (is_chromeos) {
diff --git a/content/web_test/BUILD.gn b/content/web_test/BUILD.gn
index 7a9360beb22370b61d80f8a84f6b1f96d2d77c3b..708c61c16e7baa9fcc2124722714d7d908bd5345 100644
--- a/content/web_test/BUILD.gn
+++ b/content/web_test/BUILD.gn
@@ -221,6 +221,7 @@ static_library("web_test_browser") {
     "//ui/gl",
     "//ui/shell_dialogs",
     "//url",
+    "//electron/build/config:generate_mas_config",
   ]
 
   if (is_mac) {
diff --git a/device/bluetooth/BUILD.gn b/device/bluetooth/BUILD.gn
index 3504d7197bd3225b6b83d7e057f389d8327b9ff7..92547d8bc700f3139f4bbc77d621152e0bc2a81c 100644
--- a/device/bluetooth/BUILD.gn
+++ b/device/bluetooth/BUILD.gn
@@ -257,6 +257,7 @@ component("bluetooth") {
       "CoreBluetooth.framework",
       "Foundation.framework",
     ]
+    deps += ["//electron/build/config:generate_mas_config"]
   }
 
   if (is_mac) {
diff --git a/device/bluetooth/bluetooth_adapter_mac.mm b/device/bluetooth/bluetooth_adapter_mac.mm
index f300e8d331057e894b43b74944e5052c39206844..4ff5277d550485cd79c5b5316d89c730ba709254 100644
--- a/device/bluetooth/bluetooth_adapter_mac.mm
+++ b/device/bluetooth/bluetooth_adapter_mac.mm
@@ -39,7 +39,9 @@
 #include "device/bluetooth/bluetooth_discovery_session_outcome.h"
 #include "device/bluetooth/bluetooth_socket_mac.h"
 #include "device/bluetooth/public/cpp/bluetooth_address.h"
+#include "electron/mas.h"
 
+#if !IS_MAS_BUILD()
 extern "C" {
 // Undocumented IOBluetooth Preference API [1]. Used by `blueutil` [2] and
 // `Karabiner` [3] to programmatically control the Bluetooth state. Calling the
@@ -53,6 +55,7 @@
 // [4] https://support.apple.com/kb/PH25091
 void IOBluetoothPreferenceSetControllerPowerState(int state);
 }
+#endif
 
 // A simple helper class that forwards any Bluetooth device connect notification
 // to its wrapped |_adapter|.
@@ -162,8 +165,10 @@ bool IsDeviceSystemPaired(const std::string& device_address) {
     : controller_state_function_(
           base::BindRepeating(&BluetoothAdapterMac::GetHostControllerState,
                               base::Unretained(this))),
+#if !IS_MAS_BUILD()
       power_state_function_(
           base::BindRepeating(IOBluetoothPreferenceSetControllerPowerState)),
+#endif
       device_paired_status_callback_(
           base::BindRepeating(&IsDeviceSystemPaired)) {
 }
@@ -314,8 +319,12 @@ bool IsDeviceSystemPaired(const std::string& device_address) {
 }
 
 bool BluetoothAdapterMac::SetPoweredImpl(bool powered) {
+#if !IS_MAS_BUILD()
   power_state_function_.Run(base::strict_cast<int>(powered));
   return true;
+#else
+  return false;
+#endif
 }
 
 base::WeakPtr<BluetoothLowEnergyAdapterApple>
diff --git a/gpu/ipc/service/BUILD.gn b/gpu/ipc/service/BUILD.gn
index 03a74b7d29f12be3a5d208b43beaa13f47a8e4a6..d36254ca28c1a3a4ef2b15cfbb3272129588cc20 100644
--- a/gpu/ipc/service/BUILD.gn
+++ b/gpu/ipc/service/BUILD.gn
@@ -125,6 +125,7 @@ component("service") {
         "QuartzCore.framework",
       ]
       defines += [ "GL_SILENCE_DEPRECATION" ]
+      deps += ["//electron/build/config:generate_mas_config"]
     }
     if (is_ios) {
       sources += [ "image_transport_surface_ios.mm" ]
diff --git a/gpu/ipc/service/image_transport_surface_overlay_mac.h b/gpu/ipc/service/image_transport_surface_overlay_mac.h
index 8b7a675d95ad36cbb9528bc5bc7ef05e5124e5a3..ed6a9a326b82b177059317dc4bc54b102f9bcc78 100644
--- a/gpu/ipc/service/image_transport_surface_overlay_mac.h
+++ b/gpu/ipc/service/image_transport_surface_overlay_mac.h
@@ -8,6 +8,7 @@
 #include <vector>
 
 #include "base/memory/weak_ptr.h"
+#include "electron/mas.h"
 #include "gpu/ipc/service/command_buffer_stub.h"
 #include "gpu/ipc/service/image_transport_surface.h"
 #include "ui/gfx/ca_layer_result.h"
@@ -27,7 +28,9 @@
 #include <BrowserEngineKit/BrowserEngineKit.h>
 #endif
 
+#if !IS_MAS_BUILD()
 @class CAContext;
+#endif
 @class CALayer;
 
 namespace ui {
diff --git a/media/audio/BUILD.gn b/media/audio/BUILD.gn
index 0d5c59a4946b3d3dd992cb15162fc8ed2bc17a99..8eb798f03771d2dbdaebb0ef5f781ef4fc0336e8 100644
--- a/media/audio/BUILD.gn
+++ b/media/audio/BUILD.gn
@@ -203,6 +203,7 @@ source_set("audio") {
       "CoreMedia.framework",
     ]
     weak_frameworks = [ "ScreenCaptureKit.framework" ]  # macOS 13.0
+    deps += ["//electron/build/config:generate_mas_config"]
   }
 
   if (is_ios) {
diff --git a/media/audio/apple/audio_low_latency_input.cc b/media/audio/apple/audio_low_latency_input.cc
index 97477a88340a7ae10e109d47bf5c7072b900964d..60cab6dca22061157311af6c033c9fa04218916f 100644
--- a/media/audio/apple/audio_low_latency_input.cc
+++ b/media/audio/apple/audio_low_latency_input.cc
@@ -30,6 +30,7 @@
 #include "base/strings/sys_string_conversions.h"
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
+#include "electron/mas.h"
 #include "media/audio/apple/audio_manager_apple.h"
 #include "media/audio/apple/scoped_audio_unit.h"
 #include "media/base/audio_bus.h"
@@ -43,19 +44,23 @@
 
 namespace {
 extern "C" {
+#if !IS_MAS_BUILD()
 // See:
 // https://trac.webkit.org/browser/webkit/trunk/Source/WebCore/PAL/pal/spi/cf/CoreAudioSPI.h?rev=228264
 OSStatus AudioDeviceDuck(AudioDeviceID inDevice,
                          Float32 inDuckedLevel,
                          const AudioTimeStamp* __nullable inStartTime,
                          Float32 inRampDuration) __attribute__((weak_import));
+#endif
 }
 
 void UndoDucking(AudioDeviceID output_device_id) {
+#if !IS_MAS_BUILD()
   if (AudioDeviceDuck != nullptr) {
     // Ramp the volume back up over half a second.
     AudioDeviceDuck(output_device_id, 1.0, nullptr, 0.5);
   }
+#endif
 }
 }  // namespace
 #endif
diff --git a/net/dns/BUILD.gn b/net/dns/BUILD.gn
index c83337113e00bea81e6e79070ffd94b79a1d3162..c520f0645a804bbbbc1b6ea755fe458e484e836d 100644
--- a/net/dns/BUILD.gn
+++ b/net/dns/BUILD.gn
@@ -197,6 +197,8 @@ source_set("dns") {
     ":host_resolver_manager",
     ":mdns_client",
   ]
+
+  deps += ["//electron/build/config:generate_mas_config"]
 }
 
 # The standard API of net/dns.
diff --git a/net/dns/dns_config_service_posix.cc b/net/dns/dns_config_service_posix.cc
index f863fceb0b35555e4c3bc334c0c082bb2bed2a97..1120297f383826523d9131a73eea7b956375d76c 100644
--- a/net/dns/dns_config_service_posix.cc
+++ b/net/dns/dns_config_service_posix.cc
@@ -24,6 +24,7 @@
 #include "base/threading/scoped_blocking_call.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
+#include "electron/mas.h"
 #include "net/base/ip_endpoint.h"
 #include "net/dns/dns_config.h"
 #include "net/dns/dns_hosts.h"
@@ -131,8 +132,8 @@ class DnsConfigServicePosix::Watcher : public DnsConfigService::Watcher {
 
   bool Watch() override {
     CheckOnCorrectSequence();
-
     bool success = true;
+#if !IS_MAS_BUILD()
     if (!config_watcher_.Watch(base::BindRepeating(&Watcher::OnConfigChanged,
                                                    base::Unretained(this)))) {
       LOG(ERROR) << "DNS config watch failed to start.";
@@ -149,6 +150,7 @@ class DnsConfigServicePosix::Watcher : public DnsConfigService::Watcher {
       success = false;
     }
 #endif  // !BUILDFLAG(IS_IOS)
+#endif
     return success;
   }
 
diff --git a/sandbox/mac/BUILD.gn b/sandbox/mac/BUILD.gn
index d145bdb3f879ae7e2d77f3b58fe7abd09d6f7255..8973f310aa62b59bc829e8e0f8ed068bfffa3f2b 100644
--- a/sandbox/mac/BUILD.gn
+++ b/sandbox/mac/BUILD.gn
@@ -25,6 +25,7 @@ component("seatbelt") {
   libs = [ "sandbox" ]
   deps = [ ":seatbelt_export" ]
   defines = [ "SEATBELT_IMPLEMENTATION" ]
+  deps += ["//electron/build/config:generate_mas_config"]
 }
 
 component("seatbelt_extension") {
@@ -38,6 +39,7 @@ component("seatbelt_extension") {
   libs = [ "sandbox" ]
   public_deps = [ "//base" ]
   defines = [ "SEATBELT_IMPLEMENTATION" ]
+  deps += ["//electron/build/config:generate_mas_config"]
 }
 
 component("system_services") {
@@ -52,6 +54,7 @@ component("system_services") {
   deps = [ ":seatbelt_export" ]
   public_deps = [ "//base" ]
   defines = [ "SEATBELT_IMPLEMENTATION" ]
+  deps += ["//electron/build/config:generate_mas_config"]
 }
 
 source_set("sandbox_unittests") {
diff --git a/sandbox/mac/sandbox_logging.cc b/sandbox/mac/sandbox_logging.cc
index 950cf7cfee4e11766dccf5c0bf3f15a8562f0f1e..2d99498b83180f1aa4b79cfab0ea2b1f27080106 100644
--- a/sandbox/mac/sandbox_logging.cc
+++ b/sandbox/mac/sandbox_logging.cc
@@ -21,6 +21,7 @@
 #include <string>
 
 #include "build/build_config.h"
+#include "electron/mas.h"
 #include "sandbox/mac/sandbox_crash_message.h"
 
 #if defined(ARCH_CPU_X86_64)
@@ -38,9 +39,11 @@
   }
 #endif
 
+#if !IS_MAS_BUILD()
 extern "C" {
 void abort_report_np(const char*, ...);
 }
+#endif
 
 namespace sandbox::logging {
 
@@ -82,7 +85,12 @@ void SendOsLog(Level level, const char* message) {
   }
 
   if (level == Level::FATAL) {
+#if !IS_MAS_BUILD()
     abort_report_np(message);
+#else
+    os_log_fault(OS_LOG_DEFAULT, "%s", message);
+    abort();
+#endif
   }
 }
 
diff --git a/sandbox/mac/sandbox_serializer.cc b/sandbox/mac/sandbox_serializer.cc
index 0e6e650f88e6aadd46bec96a8b41768c37d7cc6a..a6830e3f886e408c254ccd1c2b1d5c15cd3bcb92 100644
--- a/sandbox/mac/sandbox_serializer.cc
+++ b/sandbox/mac/sandbox_serializer.cc
@@ -8,6 +8,7 @@
 #include <string>
 #include <vector>
 
+#include "electron/mas.h"
 #include "sandbox/mac/sandbox_logging.h"
 #include "sandbox/mac/seatbelt.h"
 
@@ -193,6 +194,7 @@ SandboxSerializer::DeserializePolicy(const std::string& serialized_policy,
 // static
 bool SandboxSerializer::ApplySerializedPolicy(
     const std::string& serialized_policy) {
+#if !IS_MAS_BUILD()
   std::string error;
   std::optional<DeserializedPolicy> deserialized_policy =
       DeserializePolicy(serialized_policy, error);
@@ -223,6 +225,9 @@ bool SandboxSerializer::ApplySerializedPolicy(
       break;
   }
   return true;
+#else
+  return true;
+#endif
 }
 
 }  // namespace sandbox
diff --git a/sandbox/mac/seatbelt.cc b/sandbox/mac/seatbelt.cc
index e9321ba5fc0f1b24b2d990ecb27c8aaa1c8b970b..51df9671a507acd115f09a50c2d6e987fb4183c2 100644
--- a/sandbox/mac/seatbelt.cc
+++ b/sandbox/mac/seatbelt.cc
@@ -4,6 +4,8 @@
 
 #include "sandbox/mac/seatbelt.h"
 
+#include "electron/mas.h"
+
 #include <errno.h>
 #include <unistd.h>
 
@@ -12,7 +14,7 @@
 
 extern "C" {
 #include <sandbox.h>
-
+#if !IS_MAS_BUILD()
 int sandbox_init_with_parameters(const char* profile,
                                  uint64_t flags,
                                  const char* const parameters[],
@@ -58,13 +60,14 @@ sandbox_profile_t* sandbox_compile_string(const char* data,
                                           char** error);
 int sandbox_apply(sandbox_profile_t*);
 void sandbox_free_profile(sandbox_profile_t*);
-
+#endif
 }  // extern "C"
 
 namespace sandbox {
 
 namespace {
 
+#if !IS_MAS_BUILD()
 // `managed_errorbuf` uses a unique_ptr with a deleter to ensure that memory is
 // freed using the sandbox library's deallocation function to prevent unexpected
 // behavior.
@@ -107,36 +110,48 @@ bool HandleSandboxErrno(int rv, const char* message, std::string* error) {
   }
   return false;
 }
-
+#endif
 }  // namespace
 
 // static
 Seatbelt::Parameters Seatbelt::Parameters::Create() {
   Parameters params;
+#if !IS_MAS_BUILD()
   params.params_ = ::sandbox_create_params();
+#endif
   return params;
 }
 
 Seatbelt::Parameters::Parameters() = default;
 
 Seatbelt::Parameters::Parameters(Seatbelt::Parameters&& other) {
+#if !IS_MAS_BUILD()
   params_ = std::exchange(other.params_, nullptr);
+#endif
 }
 
 Seatbelt::Parameters& Seatbelt::Parameters::operator=(
     Seatbelt::Parameters&& other) {
+#if !IS_MAS_BUILD()
   params_ = std::exchange(other.params_, nullptr);
+#endif
   return *this;
 }
 
 bool Seatbelt::Parameters::Set(const char* key, const char* value) {
+#if !IS_MAS_BUILD()
   return ::sandbox_set_param(params_, key, value) == 0;
+#else
+  return true;
+#endif
 }
 
 Seatbelt::Parameters::~Parameters() {
+#if !IS_MAS_BUILD()
   if (params_) {
     ::sandbox_free_params(params_);
   }
+#endif
 }
 
 // Initialize the static member variables.
@@ -147,6 +162,7 @@ const char* Seatbelt::kProfilePureComputation = kSBXProfilePureComputation;
 
 // static
 bool Seatbelt::Init(const char* profile, uint64_t flags, std::string* error) {
+#if !IS_MAS_BUILD()
 // OS X deprecated these functions, but did not provide a suitable replacement,
 // so ignore the deprecation warning.
 #pragma clang diagnostic push
@@ -156,6 +172,9 @@ bool Seatbelt::Init(const char* profile, uint64_t flags, std::string* error) {
   return HandleSandboxResult(
       rv, std::unique_ptr<char, sandbox_error_deleter>(errorbuf), error);
 #pragma clang diagnostic pop
+#else
+  return true;
+#endif
 }
 
 // static
@@ -163,17 +182,22 @@ bool Seatbelt::InitWithParams(const std::string& profile,
                               uint64_t flags,
                               const std::vector<std::string>& parameters,
                               std::string* error) {
+#if !IS_MAS_BUILD()
   std::vector<const char*> weak_params;
   for (const std::string& param : parameters) {
     weak_params.push_back(param.c_str());
   }
   // The parameters array must be null terminated.
   weak_params.push_back(nullptr);
+
   char* errorbuf = nullptr;
   int rv = ::sandbox_init_with_parameters(profile.c_str(), flags,
                                           weak_params.data(), &errorbuf);
   return HandleSandboxResult(
       rv, std::unique_ptr<char, sandbox_error_deleter>(errorbuf), error);
+#else
+  return true;
+#endif
 }
 
 // static
@@ -181,6 +205,7 @@ bool Seatbelt::Compile(const char* profile,
                        const Seatbelt::Parameters& params,
                        std::string& compiled_profile,
                        std::string* error) {
+#if !IS_MAS_BUILD()
   char* errorbuf = nullptr;
   sandbox_profile_t* sandbox_profile =
       ::sandbox_compile_string(profile, params.params(), &errorbuf);
@@ -192,23 +217,32 @@ bool Seatbelt::Compile(const char* profile,
   compiled_profile.assign(reinterpret_cast<const char*>(sandbox_profile->data),
                           sandbox_profile->size);
   ::sandbox_free_profile(sandbox_profile);
+#endif
   return true;
 }
 
 // static
 bool Seatbelt::ApplyCompiledProfile(const std::string& profile,
                                     std::string* error) {
+#if !IS_MAS_BUILD()
   sandbox_profile_t sbox_profile = {
       .builtin = nullptr,
       .data = reinterpret_cast<const uint8_t*>(profile.data()),
       .size = profile.size()};
   return HandleSandboxErrno(::sandbox_apply(&sbox_profile),
                             "sandbox_apply: ", error);
+#else
+  return true;
+#endif
 }
 
 // static
 bool Seatbelt::IsSandboxed() {
+#if !IS_MAS_BUILD()
   return ::sandbox_check(getpid(), NULL, 0);
+#else
+  return true;
+#endif
 }
 
 }  // namespace sandbox
diff --git a/sandbox/mac/seatbelt_extension.cc b/sandbox/mac/seatbelt_extension.cc
index 79edca9ca521d1bc2ff343967348eb98039b292a..23f9410ee66024e2c6b0b6b2b356a67b0ae2eba7 100644
--- a/sandbox/mac/seatbelt_extension.cc
+++ b/sandbox/mac/seatbelt_extension.cc
@@ -9,8 +9,10 @@
 #include "base/check.h"
 #include "base/memory/ptr_util.h"
 #include "base/notreached.h"
+#include "electron/mas.h"
 #include "sandbox/mac/seatbelt_extension_token.h"
 
+#if !IS_MAS_BUILD()
 // libsandbox private API.
 extern "C" {
 extern const char* APP_SANDBOX_READ;
@@ -22,6 +24,7 @@ char* sandbox_extension_issue_file(const char* type,
                                    const char* path,
                                    uint32_t flags);
 }
+#endif
 
 namespace sandbox {
 
@@ -50,7 +53,11 @@ std::unique_ptr<SeatbeltExtension> SeatbeltExtension::FromToken(
 
 bool SeatbeltExtension::Consume() {
   DCHECK(!token_.empty());
+#if !IS_MAS_BUILD()
   handle_ = sandbox_extension_consume(token_.c_str());
+#else
+  handle_ = -1;
+#endif
   return handle_ > 0;
 }
 
@@ -62,7 +69,11 @@ bool SeatbeltExtension::ConsumePermanently() {
 }
 
 bool SeatbeltExtension::Revoke() {
+#if !IS_MAS_BUILD()
   int rv = sandbox_extension_release(handle_);
+#else
+  int rv = -1;
+#endif
   handle_ = 0;
   token_.clear();
   return rv == 0;
@@ -80,12 +91,14 @@ SeatbeltExtension::SeatbeltExtension(const std::string& token)
 char* SeatbeltExtension::IssueToken(SeatbeltExtension::Type type,
                                     const std::string& resource) {
   switch (type) {
+#if !IS_MAS_BUILD()
     case FILE_READ:
       return sandbox_extension_issue_file(APP_SANDBOX_READ, resource.c_str(),
                                           0);
     case FILE_READ_WRITE:
       return sandbox_extension_issue_file(APP_SANDBOX_READ_WRITE,
                                           resource.c_str(), 0);
+#endif
     default:
       NOTREACHED();
   }
diff --git a/sandbox/mac/system_services.cc b/sandbox/mac/system_services.cc
index eb81a70e4d5d5cd3e6ae9b45f8cd1c795ea76c51..9921ccb10d3455600eddd85f77f10228016389af 100644
--- a/sandbox/mac/system_services.cc
+++ b/sandbox/mac/system_services.cc
@@ -8,7 +8,9 @@
 #include <CoreFoundation/CoreFoundation.h>
 
 #include "base/apple/osstatus_logging.h"
+#include "electron/mas.h"
 
+#if !IS_MAS_BUILD()
 extern "C" {
 OSStatus SetApplicationIsDaemon(Boolean isDaemon);
 void _LSSetApplicationLaunchServicesServerConnectionStatus(
@@ -19,10 +21,12 @@ void _LSSetApplicationLaunchServicesServerConnectionStatus(
 // https://github.com/WebKit/WebKit/blob/24aaedc770d192d03a07ba4a71727274aaa8fc07/Source/WebKit/WebProcess/cocoa/WebProcessCocoa.mm#L840
 void _CSCheckFixDisable();
 }  // extern "C"
+#endif
 
 namespace sandbox {
 
 void DisableLaunchServices() {
+  #if !IS_MAS_BUILD()
   // Allow the process to continue without a LaunchServices ASN. The
   // INIT_Process function in HIServices will abort if it cannot connect to
   // launchservicesd to get an ASN. By setting this flag, HIServices skips
@@ -36,10 +40,13 @@ void DisableLaunchServices() {
       0, ^bool(CFDictionaryRef options) {
         return false;
       });
+  #endif
 }
 
 void DisableCoreServicesCheckFix() {
+#if !IS_MAS_BUILD()
   _CSCheckFixDisable();
+#endif
 }
 
 }  // namespace sandbox
diff --git a/third_party/blink/renderer/core/BUILD.gn b/third_party/blink/renderer/core/BUILD.gn
index c8135570f00e9bd737bd775478ea5a8642507d7a..44265e4f5a7c3bcafe26e6ee1db83bbd048e6ebf 100644
--- a/third_party/blink/renderer/core/BUILD.gn
+++ b/third_party/blink/renderer/core/BUILD.gn
@@ -439,6 +439,7 @@ component("core") {
     "//ui/gfx/geometry",
     "//ui/gfx/geometry:geometry_skia",
     "//ui/strings",
+    "//electron/build/config:generate_mas_config",
   ]
 
   if (is_mac) {
diff --git a/third_party/blink/renderer/core/editing/build.gni b/third_party/blink/renderer/core/editing/build.gni
index 4f04476e9175bae9e89eb9ea4316bffe49a9eb91..e77615c7b26518f4930ac1b004b413173fa0f46b 100644
--- a/third_party/blink/renderer/core/editing/build.gni
+++ b/third_party/blink/renderer/core/editing/build.gni
@@ -362,10 +362,14 @@ blink_core_sources_editing = [
 if (is_mac) {
   blink_core_sources_editing += [
     "commands/smart_replace_cf.cc",
-    "kill_ring_mac.mm",
     "substring_util.h",
     "substring_util.mm",
   ]
+  if (is_mas_build) {
+    blink_core_sources_editing += [ "kill_ring_mac.mm" ]
+  } else {
+    blink_core_sources_editing += [ "kill_ring_none.cc" ]
+  }
 } else {
   blink_core_sources_editing += [ "kill_ring_none.cc" ]
 }
diff --git a/third_party/blink/renderer/core/editing/kill_ring_mac.mm b/third_party/blink/renderer/core/editing/kill_ring_mac.mm
index 94afefcee81b87c05bf9b1199d90d3d4b5ea84a6..3e3aaea0ec6c8fad0d90a931d269af3af01ab73a 100644
--- a/third_party/blink/renderer/core/editing/kill_ring_mac.mm
+++ b/third_party/blink/renderer/core/editing/kill_ring_mac.mm
@@ -25,8 +25,11 @@
 
 #import "third_party/blink/renderer/core/editing/kill_ring.h"
 
+#include "electron/mas.h"
+
 namespace blink {
 
+#if !IS_MAS_BUILD()
 extern "C" {
 
 // Kill ring calls. Would be better to use NSKillRing.h, but that's not
@@ -39,7 +42,9 @@
 void _NSNewKillRingSequence();
 void _NSSetKillRingToYankedState();
 }
+#endif  // !IS_MAS_BUILD()
 
+#if !IS_MAS_BUILD()
 static void InitializeKillRingIfNeeded() {
   static bool initialized_kill_ring = false;
   if (!initialized_kill_ring) {
@@ -47,30 +52,43 @@ static void InitializeKillRingIfNeeded() {
     _NSInitializeKillRing();
   }
 }
+#endif  // !IS_MAS_BUILD()
 
 void KillRing::Append(const String& string) {
+#if !IS_MAS_BUILD()
   InitializeKillRingIfNeeded();
   _NSAppendToKillRing(string);
+#endif  // !IS_MAS_BUILD()
 }
 
 void KillRing::Prepend(const String& string) {
+#if !IS_MAS_BUILD()
   InitializeKillRingIfNeeded();
   _NSPrependToKillRing(string);
+#endif  // !IS_MAS_BUILD()
 }
 
 String KillRing::Yank() {
+#if !IS_MAS_BUILD()
   InitializeKillRingIfNeeded();
   return _NSYankFromKillRing();
+#else
+  return String();
+#endif  // !IS_MAS_BUILD()
 }
 
 void KillRing::StartNewSequence() {
+#if !IS_MAS_BUILD()
   InitializeKillRingIfNeeded();
   _NSNewKillRingSequence();
+#endif  // !IS_MAS_BUILD()
 }
 
 void KillRing::SetToYankedState() {
+#if !IS_MAS_BUILD()
   InitializeKillRingIfNeeded();
   _NSSetKillRingToYankedState();
+#endif  // !IS_MAS_BUILD()
 }
 
 }  // namespace blink
diff --git a/third_party/blink/renderer/platform/fonts/mac/font_matcher_mac.mm b/third_party/blink/renderer/platform/fonts/mac/font_matcher_mac.mm
index a4cc39ba2796d3108ff6674e60dcf5302c1da7d7..3aa68d45e2c17fe52b6c6cc5527af7dd42ad0c3a 100644
--- a/third_party/blink/renderer/platform/fonts/mac/font_matcher_mac.mm
+++ b/third_party/blink/renderer/platform/fonts/mac/font_matcher_mac.mm
@@ -37,6 +37,7 @@
 #include "base/apple/bridging.h"
 #include "base/apple/foundation_util.h"
 #include "base/apple/scoped_cftyperef.h"
+#include "electron/mas.h"
 #include "third_party/blink/renderer/platform/fonts/font_cache.h"
 #include "third_party/blink/renderer/platform/fonts/font_selection_types.h"
 #include "third_party/blink/renderer/platform/runtime_enabled_features.h"
@@ -60,8 +61,10 @@
 // We don't need localized variation axis name, so we can use
 // `CTFontCopyVariationAxesInternal()` instead.
 // Request for public API: FB13788219.
+#if !IS_MAS_BUILD()
 extern "C" CFArrayRef CTFontCopyVariationAxesInternal(CTFontRef)
     CT_AVAILABLE(macos(12.1));
+#endif
 
 namespace blink {
 
@@ -403,12 +406,16 @@ void ClampVariationValuesToFontAcceptableRange(
   // we are enabling it only on MacOS 13+ because these are our benchmarking
   // platforms.
   NSArray* all_axes;
+#if !IS_MAS_BUILD()
   if (@available(macOS 13.0, *)) {
     all_axes =
         CFToNSOwnershipCast(CTFontCopyVariationAxesInternal(ct_font.get()));
   } else {
     all_axes = CFToNSOwnershipCast(CTFontCopyVariationAxes(ct_font.get()));
   }
+#else
+  all_axes = CFToNSOwnershipCast(CTFontCopyVariationAxes(ct_font.get()));
+#endif
   if (!all_axes) {
     return;
   }
diff --git a/ui/accelerated_widget_mac/BUILD.gn b/ui/accelerated_widget_mac/BUILD.gn
index 0f8a6f75b7f01029adc2f5fd23559bacce19cf72..cf66c2f4f02a8e21cc83c3b7389fc5156bcd93ba 100644
--- a/ui/accelerated_widget_mac/BUILD.gn
+++ b/ui/accelerated_widget_mac/BUILD.gn
@@ -83,6 +83,7 @@ component("accelerated_widget_mac") {
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gl",
+    "//electron/build/config:generate_mas_config",
   ]
 }
 
diff --git a/ui/accelerated_widget_mac/ca_layer_tree_coordinator.h b/ui/accelerated_widget_mac/ca_layer_tree_coordinator.h
index d5f35d2ccfb21b231e235dbfae3eee96a488eb20..14592180823131ca87bc95300c8d9a82451e6628 100644
--- a/ui/accelerated_widget_mac/ca_layer_tree_coordinator.h
+++ b/ui/accelerated_widget_mac/ca_layer_tree_coordinator.h
@@ -8,13 +8,16 @@
 #include <queue>
 
 #include "base/containers/queue.h"
+#include "electron/mas.h"
 #include "ui/accelerated_widget_mac/accelerated_widget_mac_export.h"
 #include "ui/gfx/ca_layer_result.h"
 #include "ui/gfx/presentation_feedback.h"
 #include "ui/gl/gl_context.h"
 #include "ui/gl/presenter.h"
 
+#if !IS_MAS_BUILD()
 @class CAContext;
+#endif
 @class CALayer;
 @protocol MTLDevice;
 
@@ -119,7 +122,9 @@ class ACCELERATED_WIDGET_MAC_EXPORT CALayerTreeCoordinator {
   // both the current tree and the pending trees.
   size_t presented_ca_layer_trees_max_length_ = 2;
 
+#if !IS_MAS_BUILD()
   CAContext* __strong ca_context_;
+#endif
 
   // The root CALayer to display the current frame. This does not change
   // over the lifetime of the object.
diff --git a/ui/accelerated_widget_mac/ca_layer_tree_coordinator.mm b/ui/accelerated_widget_mac/ca_layer_tree_coordinator.mm
index 5e50feb42b4a49b03a75b510bb3ddc269282aa2f..1519401a362530b7107eab17c28b63486e7455ff 100644
--- a/ui/accelerated_widget_mac/ca_layer_tree_coordinator.mm
+++ b/ui/accelerated_widget_mac/ca_layer_tree_coordinator.mm
@@ -10,6 +10,7 @@
 #include "base/mac/mac_util.h"
 #include "base/task/single_thread_task_runner.h"
 #include "base/trace_event/trace_event.h"
+#include "electron/mas.h"
 #include "ui/accelerated_widget_mac/ca_renderer_layer_tree.h"
 #include "ui/base/cocoa/animation_utils.h"
 #include "ui/base/cocoa/remote_layer_api.h"
@@ -37,6 +38,7 @@
       buffer_presented_callback_(buffer_presented_callback),
       gl_make_current_callback_(gl_make_current_callback),
       metal_device_(metal_device) {
+#if !IS_MAS_BUILD()
   if (allow_remote_layers_) {
     root_ca_layer_ = [[CALayer alloc] init];
 #if BUILDFLAG(IS_MAC)
@@ -65,6 +67,7 @@
 #endif
     ca_context_.layer = root_ca_layer_;
   }
+#endif
 }
 
 CALayerTreeCoordinator::~CALayerTreeCoordinator() = default;
@@ -207,9 +210,13 @@
     TRACE_EVENT_INSTANT2("test_gpu", "SwapBuffers", TRACE_EVENT_SCOPE_THREAD,
                          "GLImpl", static_cast<int>(gl::GetGLImplementation()),
                          "width", pixel_size_.width());
+#if !IS_MAS_BUILD()
     if (allow_remote_layers_) {
       params.ca_context_id = [ca_context_ contextId];
     } else {
+#else
+    if (true) {
+#endif
       IOSurfaceRef io_surface = frame.layer_tree->GetContentIOSurface();
       if (io_surface) {
         DCHECK(!allow_remote_layers_);
diff --git a/ui/accelerated_widget_mac/display_ca_layer_tree.mm b/ui/accelerated_widget_mac/display_ca_layer_tree.mm
index dcf493d62990018040a3f84b6f875af737bd2214..3d1c4dcc9ee0bbfdac15f40d9c74e9f342a59e39 100644
--- a/ui/accelerated_widget_mac/display_ca_layer_tree.mm
+++ b/ui/accelerated_widget_mac/display_ca_layer_tree.mm
@@ -12,6 +12,7 @@
 #include "base/mac/mac_util.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
+#include "electron/mas.h"
 #include "ui/base/cocoa/animation_utils.h"
 #include "ui/base/cocoa/remote_layer_api.h"
 #include "ui/gfx/geometry/dip_util.h"
@@ -121,6 +122,7 @@ - (void)setContentsChanged;
 }
 
 void DisplayCALayerTree::GotCALayerFrame(uint32_t ca_context_id) {
+#if !IS_MAS_BUILD()
   // Early-out if the remote layer has not changed.
   if (remote_layer_.contextId == ca_context_id) {
     return;
@@ -150,6 +152,9 @@ - (void)setContentsChanged;
     [io_surface_layer_ removeFromSuperlayer];
     io_surface_layer_ = nil;
   }
+#else
+  NOTREACHED() << "Remote layer is being used in MAS build";
+#endif
 }
 
 void DisplayCALayerTree::GotIOSurfaceFrame(
diff --git a/ui/accessibility/platform/BUILD.gn b/ui/accessibility/platform/BUILD.gn
index 54d483d6b3f1a56573e21b1f873b8dee8fc25a0f..33bc8c9ef097a907060ed347dca2ad46b6d081f5 100644
--- a/ui/accessibility/platform/BUILD.gn
+++ b/ui/accessibility/platform/BUILD.gn
@@ -299,6 +299,7 @@ component("platform") {
         "AppKit.framework",
         "Foundation.framework",
       ]
+      deps += ["//electron/build/config:generate_mas_config"]
     }
 
     if (is_ios) {
diff --git a/ui/accessibility/platform/browser_accessibility_manager_mac.mm b/ui/accessibility/platform/browser_accessibility_manager_mac.mm
index 423fa6c7d4c9e1a17f0df2a7b1357c3424070f8e..b7e9a3ae2b5e004c670b20dff12e9bf8dd0543fb 100644
--- a/ui/accessibility/platform/browser_accessibility_manager_mac.mm
+++ b/ui/accessibility/platform/browser_accessibility_manager_mac.mm
@@ -14,6 +14,7 @@
 #include "base/task/single_thread_task_runner.h"
 #include "base/task/task_traits.h"
 #include "base/time/time.h"
+#include "electron/mas.h"
 #include "ui/accelerated_widget_mac/accelerated_widget_mac.h"
 #include "ui/accessibility/accessibility_features.h"
 #include "ui/accessibility/ax_role_properties.h"
@@ -22,7 +23,9 @@
 #include "ui/accessibility/platform/ax_private_webkit_constants_mac.h"
 #import "ui/accessibility/platform/browser_accessibility_cocoa.h"
 #import "ui/accessibility/platform/browser_accessibility_mac.h"
+#if !IS_MAS_BUILD()
 #include "ui/base/cocoa/remote_accessibility_api.h"
+#endif
 
 namespace {
 
@@ -235,6 +238,7 @@ void PostAnnouncementNotification(NSString* announcement,
         return;
       }
 
+#if !IS_MAS_BUILD()
       BrowserAccessibilityManager* root_manager = GetManagerForRootFrame();
       if (root_manager) {
         BrowserAccessibilityManagerMac* root_manager_mac =
@@ -257,6 +261,7 @@ void PostAnnouncementNotification(NSString* announcement,
           return;
         }
       }
+#endif
 
       // Use native VoiceOver support for live regions.
       BrowserAccessibilityCocoa* retained_node = native_node;
@@ -717,6 +722,7 @@ void PostAnnouncementNotification(NSString* announcement,
     return window == [NSApp accessibilityFocusedWindow];
   }
 
+#if !IS_MAS_BUILD()
   // TODO(accessibility): We need a solution to the problem described below.
   // If the window is NSAccessibilityRemoteUIElement, there are some challenges:
   // 1. NSApp is the browser which spawned the PWA, and what it considers the
@@ -745,6 +751,7 @@ void PostAnnouncementNotification(NSString* announcement,
   if ([window isKindOfClass:[NSAccessibilityRemoteUIElement class]]) {
     return true;
   }
+#endif
 
   return false;
 }
diff --git a/ui/accessibility/platform/inspect/ax_transform_mac.mm b/ui/accessibility/platform/inspect/ax_transform_mac.mm
index ef031ba14e4c649f6f3a5718ac521e6b424d64cb..38e528450196b4dbd5fa6a25b96baa10980fe73c 100644
--- a/ui/accessibility/platform/inspect/ax_transform_mac.mm
+++ b/ui/accessibility/platform/inspect/ax_transform_mac.mm
@@ -11,6 +11,7 @@
 
 #include "base/apple/foundation_util.h"
 #include "base/strings/sys_string_conversions.h"
+#include "electron/mas.h"
 #include "ui/accessibility/ax_range.h"
 #include "ui/accessibility/platform/ax_platform_node.h"
 #include "ui/accessibility/platform/ax_platform_node_cocoa.h"
@@ -111,6 +112,7 @@
     }
   }
 
+#if !IS_MAS_BUILD()
   // AXTextMarker
   if (IsAXTextMarker(value)) {
     return AXTextMarkerToBaseValue(value, indexer);
@@ -120,6 +122,7 @@
   if (IsAXTextMarkerRange(value)) {
     return AXTextMarkerRangeToBaseValue(value, indexer);
   }
+#endif
 
   // Accessible object
   if (AXElementWrapper::IsValidElement(value)) {
diff --git a/ui/base/BUILD.gn b/ui/base/BUILD.gn
index f4570ade0bc32c45e35b2d1eb11a192f3d78efd9..4da3ddf5aa20ce6320af522a04f2a251e995f610 100644
--- a/ui/base/BUILD.gn
+++ b/ui/base/BUILD.gn
@@ -355,6 +355,13 @@ component("base") {
     ]
   }
 
+  if (is_mas_build) {
+    sources -= [
+      "cocoa/remote_accessibility_api.h",
+      "cocoa/remote_accessibility_api.mm",
+    ]
+  }
+
   if (is_ios) {
     sources += [
       "device_form_factor_ios.mm",
@@ -503,6 +510,12 @@ component("base") {
     "//url",
   ]
 
+  if (is_mac) {
+    deps += [
+      "//electron/build/config:generate_mas_config"
+    ]
+  }
+
   if (is_debug || dcheck_always_on) {
     deps += [ "//third_party/re2" ]
   }
diff --git a/ui/base/cocoa/remote_accessibility_api.h b/ui/base/cocoa/remote_accessibility_api.h
index 3182458838aa96d34911280ab4c6c3aa4aa22d6d..6dc85c366b7e61c8bd0302e501c3223a19223313 100644
--- a/ui/base/cocoa/remote_accessibility_api.h
+++ b/ui/base/cocoa/remote_accessibility_api.h
@@ -10,9 +10,12 @@
 #include <vector>
 
 #include "base/component_export.h"
+#include "electron/mas.h"
 
 // NSAccessibilityRemoteUIElement is a private class in AppKit.
 
+#if !IS_MAS_BUILD()
+
 @interface NSAccessibilityRemoteUIElement : NSObject
 + (void)setRemoteUIApp:(BOOL)flag;
 + (BOOL)isRemoteUIApp;
@@ -38,4 +41,6 @@ class COMPONENT_EXPORT(UI_BASE) RemoteAccessibility {
 
 }  // namespace ui
 
+#endif  // MAS_BUILD
+
 #endif  // UI_BASE_COCOA_REMOTE_ACCESSIBILITY_API_H_
diff --git a/ui/base/cocoa/remote_layer_api.h b/ui/base/cocoa/remote_layer_api.h
index 59dc2f82214cfd883b6ebef3b0fb25af6387a9cd..912c5252d1b30d943a1552739b9eef9a8eae2d7a 100644
--- a/ui/base/cocoa/remote_layer_api.h
+++ b/ui/base/cocoa/remote_layer_api.h
@@ -9,6 +9,7 @@
 
 #include "base/component_export.h"
 #include "build/build_config.h"
+#include "electron/mas.h"
 
 #if defined(__OBJC__)
 #import <Foundation/Foundation.h>
@@ -17,6 +18,7 @@
 
 #if BUILDFLAG(IS_MAC)
 
+#if !IS_MAS_BUILD()
 // The CGSConnectionID is used to create the CAContext in the process that is
 // going to share the CALayers that it is rendering to another process to
 // display.
@@ -68,6 +70,8 @@ extern NSString* const kCAContextIgnoresHitTest;
 
 #endif  // __OBJC__
 
+#endif // MAS_BUILD
+
 namespace ui {
 
 // This function will check if all of the interfaces listed above are supported
diff --git a/ui/base/cocoa/remote_layer_api.mm b/ui/base/cocoa/remote_layer_api.mm
index 93e90c4eba9bc9b93d68e834eb6baabeb2d0ecf0..1b90f41d05f847a94adf2f4da827b1d0143b7bcf 100644
--- a/ui/base/cocoa/remote_layer_api.mm
+++ b/ui/base/cocoa/remote_layer_api.mm
@@ -5,18 +5,22 @@
 #include "ui/base/cocoa/remote_layer_api.h"
 
 #include "base/feature_list.h"
+#include "electron/mas.h"
 
 #include <objc/runtime.h>
 
 namespace ui {
 
+#if !IS_MAS_BUILD()
 namespace {
 // Control use of cross-process CALayers to display content directly from the
 // GPU process on Mac.
 BASE_FEATURE(kRemoteCoreAnimationAPI, base::FEATURE_ENABLED_BY_DEFAULT);
 }  // namespace
+#endif
 
 bool RemoteLayerAPISupported() {
+#if !IS_MAS_BUILD()
   if (!base::FeatureList::IsEnabled(kRemoteCoreAnimationAPI))
     return false;
 
@@ -53,6 +57,9 @@ bool RemoteLayerAPISupported() {
 
   // If everything is there, we should be able to use the API.
   return true;
+#else
+  return false;
+#endif  // MAS_BUILD
 }
 
 }  // namespace
diff --git a/ui/display/BUILD.gn b/ui/display/BUILD.gn
index 47da87797a4a6e2163fc356955b516d6c7a2f276..87d7cac13dfe0bd5ec91398f7fe75c0c28ef0474 100644
--- a/ui/display/BUILD.gn
+++ b/ui/display/BUILD.gn
@@ -140,6 +140,12 @@ component("display") {
     "//ui/gfx/geometry",
   ]
 
+  if (is_mac) {
+    deps += [
+      "//electron/build/config:generate_mas_config"
+    ]
+  }
+
   if (is_ios) {
     deps += [ "//build:ios_buildflags" ]
   }
diff --git a/ui/display/mac/screen_mac.mm b/ui/display/mac/screen_mac.mm
index bfffd0444b0711b201cedaddfd3edaa7b5d9220a..8cdae9f250d407d0c2d34ba7c0891b84f0113fa8 100644
--- a/ui/display/mac/screen_mac.mm
+++ b/ui/display/mac/screen_mac.mm
@@ -29,6 +29,7 @@
 #include "build/build_config.h"
 #include "components/device_event_log/device_event_log.h"
 #include "components/viz/common/resources/shared_image_format.h"
+#include "electron/mas.h"
 #include "ui/display/display.h"
 #include "ui/display/display_change_notifier.h"
 #include "ui/display/mac/screen_mac_headless.h"
@@ -179,7 +180,17 @@ DisplayMac BuildDisplayForScreen(NSScreen* screen) {
     display.set_color_depth(Display::kDefaultBitsPerPixel);
     display.set_depth_per_component(Display::kDefaultBitsPerComponent);
   }
+#if IS_MAS_BUILD()
+  // This is equivalent to the CGDisplayUsesForceToGray() API as at 2018-08-06,
+  // but avoids usage of the private API.
+  CFStringRef app = CFSTR("com.apple.CoreGraphics");
+  CFStringRef key = CFSTR("DisplayUseForcedGray");
+  Boolean key_valid = false;
+  display.set_is_monochrome(
+      CFPreferencesGetAppBooleanValue(key, app, &key_valid));
+#else
   display.set_is_monochrome(CGDisplayUsesForceToGray());
+#endif
 
   // Query the display's refresh rate.
   display.set_display_frequency(screen.maximumFramesPerSecond);
diff --git a/ui/gfx/BUILD.gn b/ui/gfx/BUILD.gn
index 26cd4350c26f79661e607e3856644704c395b9ab..9f8c78bc9abcc7ac23462c3c79d58b777278730f 100644
--- a/ui/gfx/BUILD.gn
+++ b/ui/gfx/BUILD.gn
@@ -284,6 +284,8 @@ component("gfx") {
       "CoreGraphics.framework",
       "CoreText.framework",
     ]
+
+    deps += ["//electron/build/config:generate_mas_config"]
   }
   if (is_ios) {
     sources += [
diff --git a/ui/gfx/platform_font_mac.mm b/ui/gfx/platform_font_mac.mm
index bbe355cf69f160866188216cc274d75bd35603db..06ee100d7ea2e892dbf3c0b1adc96c5013ef678a 100644
--- a/ui/gfx/platform_font_mac.mm
+++ b/ui/gfx/platform_font_mac.mm
@@ -19,6 +19,7 @@
 #include "base/numerics/safe_conversions.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
+#include "electron/mas.h"
 #include "third_party/skia/include/ports/SkTypeface_mac.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/font.h"
@@ -28,9 +29,11 @@
 
 using Weight = Font::Weight;
 
+#if !IS_MAS_BUILD()
 extern "C" {
 bool CTFontDescriptorIsSystemUIFont(CTFontDescriptorRef);
 }
+#endif
 
 namespace {
 
@@ -250,7 +253,13 @@ CTFontRef SystemFontForConstructorOfType(
   // TODO(avi, etienneb): Figure out this font stuff.
   base::apple::ScopedCFTypeRef<CTFontDescriptorRef> descriptor(
       CTFontCopyFontDescriptor(font));
+#if IS_MAS_BUILD()
+  CFNumberRef priority = (CFNumberRef)CTFontDescriptorCopyAttribute(descriptor.get(), (CFStringRef)kCTFontPriorityAttribute);
+  SInt64 v;
+  if (CFNumberGetValue(priority, kCFNumberSInt64Type, &v) && v == kCTFontPrioritySystem) {
+#else
   if (CTFontDescriptorIsSystemUIFont(descriptor.get())) {
+#endif
     // Assume it's the standard system font. The fact that this much is known is
     // enough.
     return PlatformFontMac::SystemFontType::kGeneral;
diff --git a/ui/views/BUILD.gn b/ui/views/BUILD.gn
index 5cbc7acdb196ecb8dcc987b81cf774938ff8bdfe..39badc4037525eb0039d6514cc988e8df2e6c953 100644
--- a/ui/views/BUILD.gn
+++ b/ui/views/BUILD.gn
@@ -728,6 +728,8 @@ component("views") {
       "IOSurface.framework",
       "QuartzCore.framework",
     ]
+
+    deps += ["//electron/build/config:generate_mas_config"]
   }
 
   if (is_win) {
@@ -1157,6 +1159,8 @@ source_set("test_support") {
     "//ui/base/mojom:ui_base_types",
   ]
 
+  deps += ["//electron/build/config:generate_mas_config"]
+
   if (is_win) {
     sources += [
       "test/desktop_window_tree_host_win_test_api.cc",
diff --git a/ui/views/cocoa/native_widget_mac_ns_window_host.h b/ui/views/cocoa/native_widget_mac_ns_window_host.h
index fdc7eb4e4c5e8338c725f7d317559b091d8b38fe..2239b085ac7fd87fe06aef1001551f8afe8e21e4 100644
--- a/ui/views/cocoa/native_widget_mac_ns_window_host.h
+++ b/ui/views/cocoa/native_widget_mac_ns_window_host.h
@@ -19,6 +19,7 @@
 #include "components/remote_cocoa/browser/scoped_cg_window_id.h"
 #include "components/remote_cocoa/common/native_widget_ns_window.mojom.h"
 #include "components/remote_cocoa/common/native_widget_ns_window_host.mojom.h"
+#include "electron/mas.h"
 #include "mojo/public/cpp/bindings/associated_receiver.h"
 #include "mojo/public/cpp/bindings/associated_remote.h"
 #include "ui/accelerated_widget_mac/accelerated_widget_mac.h"
@@ -34,7 +35,9 @@
 #include "ui/views/window/dialog_observer.h"
 
 @class NativeWidgetMacNSWindow;
+#if !IS_MAS_BUILD()
 @class NSAccessibilityRemoteUIElement;
+#endif
 @class NSView;
 
 namespace remote_cocoa {
@@ -506,10 +509,12 @@ class VIEWS_EXPORT NativeWidgetMacNSWindowHost
   mojo::AssociatedRemote<remote_cocoa::mojom::NativeWidgetNSWindow>
       remote_ns_window_remote_;
 
+#if !IS_MAS_BUILD()
   // Remote accessibility objects corresponding to the NSWindow and its root
   // NSView.
   NSAccessibilityRemoteUIElement* __strong remote_window_accessible_;
   NSAccessibilityRemoteUIElement* __strong remote_view_accessible_;
+#endif
 
   // Used to force the NSApplication's focused accessibility element to be the
   // views::Views accessibility tree when the NSView for this is focused.
diff --git a/ui/views/cocoa/native_widget_mac_ns_window_host.mm b/ui/views/cocoa/native_widget_mac_ns_window_host.mm
index e40d0d5be1c48fc713d738f9ffb8105cce450e52..a1185e4f63de04c56448257567533764476d6c3c 100644
--- a/ui/views/cocoa/native_widget_mac_ns_window_host.mm
+++ b/ui/views/cocoa/native_widget_mac_ns_window_host.mm
@@ -20,6 +20,7 @@
 #include "components/remote_cocoa/app_shim/native_widget_ns_window_bridge.h"
 #include "components/remote_cocoa/browser/ns_view_ids.h"
 #include "components/remote_cocoa/browser/window.h"
+#include "electron/mas.h"
 #include "mojo/public/cpp/bindings/self_owned_associated_receiver.h"
 #include "ui/accelerated_widget_mac/window_resize_helper_mac.h"
 #include "ui/accessibility/accessibility_features.h"
@@ -361,8 +362,12 @@ void HandleAccelerator(const ui::Accelerator& accelerator,
   if (in_process_ns_window_bridge_) {
     return gfx::NativeViewAccessible(in_process_ns_window_bridge_->ns_view());
   }
+#if !IS_MAS_BUILD()
   return gfx::NativeViewAccessible(
       (id<NSAccessibility>)remote_view_accessible_);
+#else
+  return {};
+#endif
 }
 
 gfx::NativeViewAccessible
@@ -378,8 +383,12 @@ void HandleAccelerator(const ui::Accelerator& accelerator,
         [in_process_ns_window_bridge_->ns_view() window]);
   }
 
+#if !IS_MAS_BUILD()
   return gfx::NativeViewAccessible(
       (id<NSAccessibility>)remote_window_accessible_);
+#else
+  return {};
+#endif
 }
 
 remote_cocoa::mojom::NativeWidgetNSWindow*
@@ -1450,9 +1459,11 @@ void HandleAccelerator(const ui::Accelerator& accelerator,
   // for PWAs. However this breaks accessibility on in-process windows,
   // so set it back to NO when a local window gains focus. See
   // https://crbug.com/41485830.
+#if !IS_MAS_BUILD()
   if (is_key && features::IsAccessibilityRemoteUIAppEnabled()) {
     [NSAccessibilityRemoteUIElement setRemoteUIApp:!!application_host_];
   }
+#endif
   // Explicitly set the keyboard accessibility state on regaining key
   // window status.
   if (is_key && is_content_first_responder) {
@@ -1605,17 +1616,20 @@ void HandleAccelerator(const ui::Accelerator& accelerator,
 void NativeWidgetMacNSWindowHost::SetRemoteAccessibilityTokens(
     const std::vector<uint8_t>& window_token,
     const std::vector<uint8_t>& view_token) {
+#if !IS_MAS_BUILD()
   remote_window_accessible_ =
       ui::RemoteAccessibility::GetRemoteElementFromToken(window_token);
   remote_view_accessible_ =
       ui::RemoteAccessibility::GetRemoteElementFromToken(view_token);
   [remote_view_accessible_ setWindowUIElement:remote_window_accessible_];
   [remote_view_accessible_ setTopLevelUIElement:remote_window_accessible_];
+#endif
 }
 
 bool NativeWidgetMacNSWindowHost::GetRootViewAccessibilityToken(
     base::ProcessId* pid,
     std::vector<uint8_t>* token) {
+#if !IS_MAS_BUILD()
   *pid = getpid();
   id element_id = GetNativeViewAccessible();
 
@@ -1628,6 +1642,7 @@ void HandleAccelerator(const ui::Accelerator& accelerator,
   }
 
   *token = ui::RemoteAccessibility::GetTokenForLocalElement(element_id);
+#endif
   return true;
 }
 
diff --git a/ui/views/controls/webview/BUILD.gn b/ui/views/controls/webview/BUILD.gn
index faa860ef58afdde28e7929c99e191b06e67efad6..827372d5f2c7e72e741a1a082998e590d75935e3 100644
--- a/ui/views/controls/webview/BUILD.gn
+++ b/ui/views/controls/webview/BUILD.gn
@@ -46,6 +46,12 @@ component("webview") {
     "//url",
   ]
 
+  if (is_mac) {
+    deps += [
+      "//electron/build/config:generate_mas_config",
+    ]
+  }
+
   public_deps = [
     "//base",
     "//content/public/browser",
