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

ui/views/views_delegate.h

 // 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.
 
 #ifndef UI_VIEWS_VIEWS_DELEGATE_H_
 #define UI_VIEWS_VIEWS_DELEGATE_H_
 
 #include <string>
 
 #if defined(OS_WIN)
@@ skipping 20 matching lines @@
 class SiteInstance;
 }
 
 namespace gfx {
 class ImageSkia;
 class Rect;
 }
 
 namespace ui {
 class ContextFactory;
+class NativeTheme;
 }
 
 namespace views {
 
 class NativeWidget;
 class NonClientFrameView;
 class ViewsTouchEditingControllerFactory;
 class View;
 class Widget;
 
@@ skipping 133 matching lines @@
   // not changed, |callback| is never run.
   //
   // The return value is a bitmask of AppbarAutohideEdge.
   virtual int GetAppbarAutohideEdges(HMONITOR monitor,
                                      const base::Closure& callback);
 #endif
 
   // Returns a blocking pool task runner given a TaskRunnerType.
   virtual scoped_refptr<base::TaskRunner> GetBlockingPoolTaskRunner();
 
+  // Returns a value which, if non-null, will be used as the NativeTheme for
+  // |widget| in place of the platform default native theme.
+  virtual ui::NativeTheme* GetNativeThemeOverride(const Widget* widget);
+
  protected:
   ViewsDelegate();
 
  private:
   scoped_ptr<ViewsTouchEditingControllerFactory> views_tsc_factory_;
 
 #if defined(USE_AURA)
   scoped_ptr<TouchSelectionMenuRunnerViews> touch_selection_menu_runner_;
 #endif
 
   NativeWidgetFactory native_widget_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ViewsDelegate);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_VIEWS_DELEGATE_H_