Add app.window.alphaEnabled() and onAlphaEnabledChanged.

ui/views/widget/desktop_aura/desktop_window_tree_host_win.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_WIDGET_DESKTOP_AURA_DESKTOP_WINDOW_TREE_HOST_WIN_H_
 #define UI_VIEWS_WIDGET_DESKTOP_AURA_DESKTOP_WINDOW_TREE_HOST_WIN_H_
 
 #include "ui/aura/window_tree_host.h"
 #include "ui/views/views_export.h"
 #include "ui/views/widget/desktop_aura/desktop_window_tree_host.h"
@@ skipping 85 matching lines @@
   virtual bool IsFullscreen() const OVERRIDE;
   virtual void SetOpacity(unsigned char opacity) OVERRIDE;
   virtual void SetWindowIcons(const gfx::ImageSkia& window_icon,
                               const gfx::ImageSkia& app_icon) OVERRIDE;
   virtual void InitModalType(ui::ModalType modal_type) OVERRIDE;
   virtual void FlashFrame(bool flash_frame) OVERRIDE;
   virtual void OnRootViewLayout() const OVERRIDE;
   virtual void OnNativeWidgetFocus() OVERRIDE;
   virtual void OnNativeWidgetBlur() OVERRIDE;
   virtual bool IsAnimatingClosed() const OVERRIDE;
+  virtual bool CanHaveAlphaEnabled() const OVERRIDE;
 
   // Overridden from aura::WindowTreeHost:
   virtual ui::EventSource* GetEventSource() OVERRIDE;
   virtual gfx::AcceleratedWidget GetAcceleratedWidget() OVERRIDE;
   virtual void Show() OVERRIDE;
   virtual void Hide() OVERRIDE;
   virtual gfx::Rect GetBounds() const OVERRIDE;
   virtual void SetBounds(const gfx::Rect& bounds) OVERRIDE;
   virtual gfx::Point GetLocationOnNativeScreen() const OVERRIDE;
   virtual void SetCapture() OVERRIDE;
@@ skipping 150 matching lines @@
   static bool is_cursor_visible_;
 
   scoped_ptr<aura::client::ScopedTooltipDisabler> tooltip_disabler_;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopWindowTreeHostWin);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_DESKTOP_AURA_DESKTOP_WINDOW_TREE_HOST_WIN_H_