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

ui/views/widget/widget.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/widget/widget.h"
 
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 748 matching lines @@
       return provider;
 
     provider = root_widget->default_theme_provider_.get();
     if (provider)
       return provider;
   }
   return default_theme_provider_.get();
 }
 
 const ui::NativeTheme* Widget::GetNativeTheme() const {
+  if (ViewsDelegate::GetInstance()) {
+    ui::NativeTheme* theme =
+        ViewsDelegate::GetInstance()->GetNativeThemeOverride(this);

[sky, 2015/11/12 21:58:29]

Can we cache this rather than querying the delegate every time?

[Evan Stade, 2015/11/12 22:11:11]

I suppose we could as long as we call NativeTheme::NotifyObservers whenever the
theme changes.

+    if (theme)
+      return theme;
+  }
   return native_widget_->GetNativeTheme();
 }
 
 FocusManager* Widget::GetFocusManager() {
   Widget* toplevel_widget = GetTopLevelWidget();
   return toplevel_widget ? toplevel_widget->focus_manager_.get() : NULL;
 }
 
 const FocusManager* Widget::GetFocusManager() const {
   const Widget* toplevel_widget = GetTopLevelWidget();
@@ skipping 719 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // internal::NativeWidgetPrivate, NativeWidget implementation:
 
 internal::NativeWidgetPrivate* NativeWidgetPrivate::AsNativeWidgetPrivate() {
   return this;
 }
 
 }  // namespace internal
 }  // namespace views