[MD] Implement incognito colors as a NativeTheme (for Aura).

chrome/browser/ui/views/chrome_views_delegate.cc

Index: chrome/browser/ui/views/chrome_views_delegate.cc
diff --git a/chrome/browser/ui/views/chrome_views_delegate.cc b/chrome/browser/ui/views/chrome_views_delegate.cc
index f7efbac74c2e794339c6c16fdd2d4b342eb54fb0..6a91f0602be8578278aa4951784895328912996e 100644
--- a/chrome/browser/ui/views/chrome_views_delegate.cc
+++ b/chrome/browser/ui/views/chrome_views_delegate.cc
@@ -34,6 +34,7 @@
 #include "chrome/browser/app_icon_win.h"
 #include "content/public/browser/browser_thread.h"
 #include "ui/base/win/shell.h"
+#include "ui/native_theme/native_theme_win_dark.h"
 #endif
 
 #if defined(USE_AURA)
@@ -42,6 +43,14 @@
 #include "ui/aura/window_event_dispatcher.h"
 #endif
 
+#if defined(OS_WIN) || defined(OS_CHROMEOS)
+#include "ui/wm/core/transient_window_manager.h"
+#endif
+
+#if defined(OS_CHROMEOS)
+#include "ui/native_theme/native_theme_aura_dark.h"
+#endif
+
 #if defined(USE_AURA) && !defined(OS_CHROMEOS)
 #include "chrome/browser/ui/host_desktop.h"
 #include "ui/views/widget/desktop_aura/desktop_native_widget_aura.h"
@@ -472,6 +481,28 @@ ChromeViewsDelegate::GetBlockingPoolTaskRunner() {
   return content::BrowserThread::GetBlockingPool();
 }
 
+ui::NativeTheme* ChromeViewsDelegate::GetNativeThemeOverride(
+    const views::Widget* widget) {
+#if defined(OS_CHROMEOS) || defined(OS_WIN)
+  aura::Window* window = widget->GetNativeWindow();
+  for (aura::Window* parent = window; parent;
+       parent = wm::TransientWindowManager::Get(parent)->transient_parent()) {
+    window = parent;
+  }
+
+  views::Widget* parent_widget =
+      views::Widget::GetWidgetForNativeWindow(window);
+  Profile* profile = GetProfileForWindow(parent_widget);
+  if (profile && profile->IsOffTheRecord())
+#if defined(OS_WIN)
+    return ui::NativeThemeWinDark::instance();
+#else
+    return ui::NativeThemeAuraDark::instance();
+#endif
+#endif
+  return nullptr;
+}
+
 #if !defined(USE_AURA) && !defined(USE_CHROMEOS)
 views::Widget::InitParams::WindowOpacity
 ChromeViewsDelegate::GetOpacityForInitParams(