Add app.window.alphaEnabled() and onAlphaEnabledChanged.

ui/views/widget/native_widget_private.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_NATIVE_WIDGET_PRIVATE_H_
 #define UI_VIEWS_WIDGET_NATIVE_WIDGET_PRIVATE_H_
 
 #include "base/strings/string16.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/gfx/native_widget_types.h"
@@ skipping 209 matching lines @@
   virtual void ClearNativeFocus() = 0;
   virtual gfx::Rect GetWorkAreaBoundsInScreen() const = 0;
   virtual Widget::MoveLoopResult RunMoveLoop(
       const gfx::Vector2d& drag_offset,
       Widget::MoveLoopSource source,
       Widget::MoveLoopEscapeBehavior escape_behavior) = 0;
   virtual void EndMoveLoop() = 0;
   virtual void SetVisibilityChangedAnimationsEnabled(bool value) = 0;
   virtual ui::NativeTheme* GetNativeTheme() const = 0;
   virtual void OnRootViewLayout() const = 0;
+  virtual bool IsTranslucentWindowOpacitySupported() const = 0;
 
   // Repost an unhandled event to the native widget for default OS processing.
   virtual void RepostNativeEvent(gfx::NativeEvent native_event) = 0;
 
   // Overridden from NativeWidget:
   virtual internal::NativeWidgetPrivate* AsNativeWidgetPrivate() OVERRIDE;
 };
 
 }  // namespace internal
 }  // namespace views
 
 #endif  // UI_VIEWS_WIDGET_NATIVE_WIDGET_PRIVATE_H_