Add support for transparent background API

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/extensions/extension_icon_image.h"
@@ skipping 126 matching lines @@
   struct CreateParams {
     CreateParams();
     ~CreateParams();
 
     WindowType window_type;
     Frame frame;
 
     bool has_frame_color;
     SkColor active_frame_color;
     SkColor inactive_frame_color;
-    bool transparent_background;  // Only supported on ash.
+    bool alpha_enabled;  // Only supported on ash.
 
     // The initial content/inner bounds specification (excluding any window
     // decorations).
     BoundsSpecification content_spec;
 
     // The initial window/outer bounds specification (including window
     // decorations).
     BoundsSpecification window_spec;
 
     std::string window_key;
@@ skipping 185 matching lines @@
 
   // Whether the always-on-top property has been set by the chrome.app.window
   // API. Note that the actual value of this property in the native app window
   // may be false if the bit is silently switched off for security reasons.
   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;
 
+  // Whether this window allows a transparent background image.
+  // Currently, only Ash (ChromeOS/Windows) support transparent windows.
+  // This will always return false on platforms that don't support transparent
+  // windows.
+  bool AlphaEnabled() const;
+
  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 158 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_;
 
+  // Cache the alpha_enabled attribute from the window creation.
+  bool cached_alpha_enabled_;
+
   DISALLOW_COPY_AND_ASSIGN(AppWindow);
 };
 
 }  // namespace apps
 
 #endif  // APPS_APP_WINDOW_H_