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 c4049d94aaa00774777f3788c7093cb19101fcb5..92866fc8fe2375f9703ce77be980646bf61cf8ac 100644
--- a/ui/native_theme/native_theme.cc
+++ b/ui/native_theme/native_theme.cc
@@ -144,6 +144,8 @@ 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 03cf4a5080e77983abcf0b40b7621d33bd7005cb..a23aea98f14bb7dac8f9c5ca7df22349bf61478f 100644
--- a/ui/native_theme/native_theme.h
+++ b/ui/native_theme/native_theme.h
@@ -406,6 +406,23 @@ 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
@@ -587,6 +604,7 @@ class NATIVE_THEME_EXPORT NativeTheme {
   PageColors page_colors_ = PageColors::kOff;
   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 6230688b9ed1dcb239482cfa1dab7daeaf0501c2..aeacdc17413eb5bedb9218140755777eef27349e 100644
--- a/ui/native_theme/native_theme_win.cc
+++ b/ui/native_theme/native_theme_win.cc
@@ -621,6 +621,8 @@ 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();
 }
 
