From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Samuel Attard <sattard@slack-corp.com>
Date: Mon, 26 Aug 2019 14:32:41 -0700
Subject: feat: add set_theme_source to allow apps to override chromiums
 internal theme choice

This patch is required as Chromium doesn't currently let folks using
//ui override the theme choice in NativeTheme.  It defaults to
respecting the OS theme choice and some apps don't always want to do
that.  With this patch we can override the theme value that Chromium
uses internally for things like menus and devtools.

We can remove this patch once it has in some shape been upstreamed.

diff --git a/ui/native_theme/native_theme.cc b/ui/native_theme/native_theme.cc
index d466e72df7e2c7094ed80d6b70b78eab7a93ba4c..a9a10f2c91a473c41d5e2a0ce7ce2608894f55a8 100644
--- a/ui/native_theme/native_theme.cc
+++ b/ui/native_theme/native_theme.cc
@@ -209,6 +209,8 @@ NativeTheme::NativeTheme(bool should_use_dark_colors,
 NativeTheme::~NativeTheme() = default;
 
 bool NativeTheme::ShouldUseDarkColors() const {
+  if (theme_source() == ThemeSource::kForcedLight) return false;
+  if (theme_source() == ThemeSource::kForcedDark) return true;
   return should_use_dark_colors_;
 }
 
diff --git a/ui/native_theme/native_theme.h b/ui/native_theme/native_theme.h
index 3385e9e9d5690d746d4935f3ddc74bc09746c017..278663682017393b1cd52475d8fffb601d0cbe25 100644
--- a/ui/native_theme/native_theme.h
+++ b/ui/native_theme/native_theme.h
@@ -443,6 +443,23 @@ class NATIVE_THEME_EXPORT NativeTheme {
       scoped_refptr<ColorProviderKey::ThemeInitializerSupplier> custom_theme,
       bool use_custom_frame = true) const;
 
+
+  enum ThemeSource {
+    kSystem,
+    kForcedDark,
+    kForcedLight,
+  };
+
+  ThemeSource theme_source() const {
+    return theme_source_;
+  }
+
+  void set_theme_source(ThemeSource theme_source) {
+    bool original = ShouldUseDarkColors();
+    theme_source_ = theme_source;
+    if (ShouldUseDarkColors() != original) NotifyOnNativeThemeUpdated();
+  }
+
   // Returns a shared instance of the native theme that should be used for web
   // rendering. Do not use it in a normal application context (i.e. browser).
   // The returned object should not be deleted by the caller. This function is
@@ -672,6 +689,7 @@ class NATIVE_THEME_EXPORT NativeTheme {
   PreferredColorScheme preferred_color_scheme_ = PreferredColorScheme::kLight;
   PreferredContrast preferred_contrast_ = PreferredContrast::kNoPreference;
   std::optional<base::TimeDelta> caret_blink_interval_;
+  ThemeSource theme_source_ = ThemeSource::kSystem;
 
   SEQUENCE_CHECKER(sequence_checker_);
 };
diff --git a/ui/native_theme/native_theme_win.cc b/ui/native_theme/native_theme_win.cc
index 566230f830edec321ec3032b81e3478f155912c6..65d4d09c1e9e50197244a3e0f79ace8498463774 100644
--- a/ui/native_theme/native_theme_win.cc
+++ b/ui/native_theme/native_theme_win.cc
@@ -673,6 +673,8 @@ bool NativeThemeWin::ShouldUseDarkColors() const {
   // ...unless --force-dark-mode was specified in which case caveat emptor.
   if (InForcedColorsMode() && !IsForcedDarkMode())
     return false;
+  if (theme_source() == ThemeSource::kForcedLight) return false;
+  if (theme_source() == ThemeSource::kForcedDark) return true;
   return NativeTheme::ShouldUseDarkColors();
 }
 
