Add app.window.alphaEnabled() and onAlphaEnabledChanged.

apps/app_window.h

 // Copyright 2014 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 APPS_APP_WINDOW_H_
 #define APPS_APP_WINDOW_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/sessions/session_id.h"
@@ skipping 344 matching lines @@
   bool IsAlwaysOnTop() const;
 
   // Retrieve the current state of the app window as a dictionary, to pass to
   // the renderer.
   void GetSerializedState(base::DictionaryValue* properties) const;
 
   // Called by the window API when events can be sent to the window for this
   // app.
   void WindowEventsReady();
 
+  // Whether the app window wants a transparent background.
+  bool requested_transparent_background() const {
+    return requested_transparent_background_;
+  }
+
  protected:
   virtual ~AppWindow();
 
  private:
   // PlatformAppBrowserTest needs access to web_contents()
   friend class extensions::PlatformAppBrowserTest;
 
   // content::WebContentsDelegate implementation.
   virtual void CloseContents(content::WebContents* contents) OVERRIDE;
   virtual bool ShouldSuppressDialogs() OVERRIDE;
@@ skipping 176 matching lines @@
   // Whether the delayed Show() call was for an active or inactive window.
   ShowType delayed_show_type_;
 
   // Cache the desired value of the always-on-top property. When windows enter
   // fullscreen or overlap the Windows taskbar, this property will be
   // automatically and silently switched off for security reasons. It is
   // reinstated when the window exits fullscreen and moves away from the
   // taskbar.
   bool cached_always_on_top_;
 
+  // Whether |transparent_background| was set in the CreateParams.
+  bool requested_transparent_background_;
+
   DISALLOW_COPY_AND_ASSIGN(AppWindow);
 };
 
 }  // namespace apps
 
 #endif  // APPS_APP_WINDOW_H_