[Aura] Turns on Window opacity support.

ui/aura/window.h

 // Copyright (c) 2011 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_AURA_WINDOW_H_
 #define UI_AURA_WINDOW_H_
 #pragma once
 
 #include <vector>
 
@@ skipping 234 matching lines @@
   // Returns true if this window has a mouse capture.
   bool HasCapture();
 
   // Returns the first ancestor whose parent window returns true from
   // IsToplevelWindowContainer.
   Window* GetToplevelWindow();
 
   // Returns true if this window is fullscreen or contains a fullscreen window.
   bool IsOrContainsFullscreenWindow() const;
 
+  // Sets the opacity of the window.
+  void SetOpacity(unsigned char opacity);
+
   // Returns an animation configured with the default duration. All animations
   // should use this. Caller owns returned value.
   static ui::Animation* CreateDefaultAnimation();
 
  protected:
   // Returns the desktop or NULL if we aren't yet attached to a desktop.
   virtual Desktop* GetDesktop();
 
  private:
   friend class LayoutManager;
@@ skipping 63 matching lines @@
   bool stops_event_propagation_;
 
   ObserverList<WindowObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(Window);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_WINDOW_H_