From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Ryan Manuel <ryanm@cypress.io>
Date: Thu, 4 Aug 2022 22:37:01 -0500
Subject: Create browser v8 snapshot file name fuse

By default, chromium sets up one v8 snapshot to be used in all v8 contexts. This patch allows consumers
to have a dedicated browser process v8 snapshot defined by the file `browser_v8_context_snapshot.bin`.

diff --git a/content/app/content_main_runner_impl.cc b/content/app/content_main_runner_impl.cc
index 48d3c60ac1b5691da1b5ae28aed9fd4085f71325..1213080cce1a3d456bc2ee08024b175b2c517e30 100644
--- a/content/app/content_main_runner_impl.cc
+++ b/content/app/content_main_runner_impl.cc
@@ -39,6 +39,7 @@
 #include "base/process/memory.h"
 #include "base/process/process.h"
 #include "base/process/process_handle.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/task/single_thread_task_runner.h"
@@ -253,8 +254,13 @@ std::string GetSnapshotDataDescriptor(const base::CommandLine& command_line) {
 
 #endif
 
-void LoadV8SnapshotFile(const base::CommandLine& command_line) {
+void LoadV8SnapshotFile(const raw_ptr<ContentMainDelegate> delegate, const base::CommandLine& command_line) {
   const gin::V8SnapshotFileType snapshot_type = GetSnapshotType(command_line);
+  base::StringPiece browser_v8_snapshot_file_name = delegate->GetBrowserV8SnapshotFilename();
+  if (!browser_v8_snapshot_file_name.empty()) {
+    gin::V8Initializer::LoadV8SnapshotFromFileName(browser_v8_snapshot_file_name, snapshot_type);
+    return;
+  }
 #if BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_MAC)
   base::FileDescriptorStore& file_descriptor_store =
       base::FileDescriptorStore::GetInstance();
@@ -283,11 +289,12 @@ bool ShouldLoadV8Snapshot(const base::CommandLine& command_line,
 
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
-void LoadV8SnapshotIfNeeded(const base::CommandLine& command_line,
+void LoadV8SnapshotIfNeeded(const raw_ptr<ContentMainDelegate> delegate,
+                            const base::CommandLine& command_line,
                             const std::string& process_type) {
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
   if (ShouldLoadV8Snapshot(command_line, process_type))
-    LoadV8SnapshotFile(command_line);
+    LoadV8SnapshotFile(delegate, command_line);
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 }
 
@@ -971,7 +978,7 @@ int ContentMainRunnerImpl::Initialize(ContentMainParams params) {
     return TerminateForFatalInitializationError();
 #endif  // BUILDFLAG(IS_ANDROID) && (ICU_UTIL_DATA_IMPL == ICU_UTIL_DATA_FILE)
 
-  LoadV8SnapshotIfNeeded(command_line, process_type);
+  LoadV8SnapshotIfNeeded(delegate_, command_line, process_type);
 
   blink::TrialTokenValidator::SetOriginTrialPolicyGetter(
       base::BindRepeating([]() -> blink::OriginTrialPolicy* {
diff --git a/content/public/app/content_main_delegate.cc b/content/public/app/content_main_delegate.cc
index 610938d92786cc033c19615364e5e45d54bf8ec6..11797f0429845bd3b654aff2bfa468460e4fd772 100644
--- a/content/public/app/content_main_delegate.cc
+++ b/content/public/app/content_main_delegate.cc
@@ -5,6 +5,7 @@
 #include "content/public/app/content_main_delegate.h"
 
 #include "base/check.h"
+#include "base/strings/string_piece.h"
 #include "build/build_config.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/common/content_client.h"
@@ -87,6 +88,10 @@ std::optional<int> ContentMainDelegate::PostEarlyInitialization(
   return std::nullopt;
 }
 
+base::StringPiece ContentMainDelegate::GetBrowserV8SnapshotFilename() {
+  return base::StringPiece();
+}
+
 ContentClient* ContentMainDelegate::CreateContentClient() {
   return new ContentClient();
 }
diff --git a/content/public/app/content_main_delegate.h b/content/public/app/content_main_delegate.h
index 2b0919b9a56bd37a398109777dfd199d777a9f74..823f44ab0303ccd6c7502ec65560ddb555b551e7 100644
--- a/content/public/app/content_main_delegate.h
+++ b/content/public/app/content_main_delegate.h
@@ -10,6 +10,7 @@
 #include <string>
 #include <vector>
 
+#include "base/strings/string_piece.h"
 #include "build/build_config.h"
 #include "content/common/content_export.h"
 #include "content/public/common/main_function_params.h"
@@ -168,6 +169,8 @@ class CONTENT_EXPORT ContentMainDelegate {
   virtual bool ShouldHandleConsoleControlEvents();
 #endif
 
+  virtual base::StringPiece GetBrowserV8SnapshotFilename();
+
  protected:
   friend class ContentClientCreator;
   friend class ContentClientInitializer;
diff --git a/gin/v8_initializer.cc b/gin/v8_initializer.cc
index d069889816cbc50a922bed055c78d6779c49e03d..158a96fd3a14fe975554a0d0c40c80f090eb6490 100644
--- a/gin/v8_initializer.cc
+++ b/gin/v8_initializer.cc
@@ -577,8 +577,7 @@ void V8Initializer::GetV8ExternalSnapshotData(const char** snapshot_data_out,
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
 
-// static
-void V8Initializer::LoadV8Snapshot(V8SnapshotFileType snapshot_file_type) {
+void V8Initializer::LoadV8SnapshotFromFileName(base::StringPiece file_name, V8SnapshotFileType snapshot_file_type) {
   if (g_mapped_snapshot) {
     // TODO(crbug.com/802962): Confirm not loading different type of snapshot
     // files in a process.
@@ -587,10 +586,17 @@ void V8Initializer::LoadV8Snapshot(V8SnapshotFileType snapshot_file_type) {
 
   base::MemoryMappedFile::Region file_region;
   base::File file =
-      OpenV8File(GetSnapshotFileName(snapshot_file_type), &file_region);
+      OpenV8File(file_name.data(), &file_region);
   LoadV8SnapshotFromFile(std::move(file), &file_region, snapshot_file_type);
 }
 
+// static
+void V8Initializer::LoadV8Snapshot(V8SnapshotFileType snapshot_file_type) {
+  const char* file_name = GetSnapshotFileName(snapshot_file_type);
+
+  LoadV8SnapshotFromFileName(file_name, snapshot_file_type);
+}
+
 // static
 void V8Initializer::LoadV8SnapshotFromFile(
     base::File snapshot_file,
diff --git a/gin/v8_initializer.h b/gin/v8_initializer.h
index dd9899c3e0dbadfc0074ffce87d51193e1c963cb..25c747ee645d845a0abfaf63cc66595319df4b51 100644
--- a/gin/v8_initializer.h
+++ b/gin/v8_initializer.h
@@ -9,6 +9,7 @@
 
 #include "base/files/file.h"
 #include "base/files/memory_mapped_file.h"
+#include "base/strings/string_piece.h"
 #include "build/build_config.h"
 #include "gin/array_buffer.h"
 #include "gin/gin_export.h"
@@ -42,6 +43,7 @@ class GIN_EXPORT V8Initializer {
                                         int* snapshot_size_out);
 
 #if defined(V8_USE_EXTERNAL_STARTUP_DATA)
+  static void LoadV8SnapshotFromFileName(base::StringPiece file_name, V8SnapshotFileType snapshot_file_type);
   // Load V8 snapshot from default resources, if they are available.
   static void LoadV8Snapshot(
       V8SnapshotFileType snapshot_file_type = V8SnapshotFileType::kDefault);
