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 3f596e0d24ccf7586e2e20d219b73300ee3f56a0..0eb957667b591d1215b60f83141d8431079c1f45 100644
--- a/ui/native_theme/native_theme.cc
+++ b/ui/native_theme/native_theme.cc
@@ -124,6 +124,8 @@ 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 3b9c8841ac65471141307025394464a90b02daa9..dba57a6af6a3ce8dc258a747d721fbc9d50b0ebf 100644
--- a/ui/native_theme/native_theme.h
+++ b/ui/native_theme/native_theme.h
@@ -392,6 +392,23 @@ class NATIVE_THEME_EXPORT NativeTheme {
           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
@@ -557,6 +574,7 @@ class NATIVE_THEME_EXPORT NativeTheme {
   bool forced_colors_ = false;
   PreferredColorScheme preferred_color_scheme_ = PreferredColorScheme::kLight;
   PreferredContrast preferred_contrast_ = PreferredContrast::kNoPreference;
+  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 6b9fb74004eba57fdff396124214356f4bcf0852..70807b315f805baab2574148520323ce78f624cb 100644
--- a/ui/native_theme/native_theme_win.cc
+++ b/ui/native_theme/native_theme_win.cc
@@ -618,6 +618,8 @@ 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();
 }
 
