Add support for transparent background API

chrome/renderer/resources/extensions/app_window_custom_bindings.js

 // 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.
 
 // Custom binding for the app_window API.
 
 var appWindowNatives = requireNative('app_window_natives');
 var runtimeNatives = requireNative('runtime');
 var Binding = require('binding').Binding;
 var Event = require('event_bindings').Event;
@@ skipping 225 matching lines @@
       return appWindowData.minimized;
     };
     AppWindow.prototype.isMaximized = function() {
       return appWindowData.maximized;
     };
     AppWindow.prototype.isAlwaysOnTop = function() {
       return appWindowData.alwaysOnTop;
     };
     AppWindow.prototype.alphaEnabled = function() {
       return appWindowData.alphaEnabled;
-    }
+    };
     AppWindow.prototype.handleWindowFirstShownForTests = function(callback) {
       // This allows test apps to get have their callback run even if they
       // call this after the first show has happened.
       if (this.firstShowHasHappened) {
         callback();
         return;
       }
       this.onWindowFirstShownForTests.addListener(callback);
     }
 
@@ skipping 135 matching lines @@
       constraints[key] = 0;
   });
 
   currentWindowInternal.setSizeConstraints(boundsType, constraints);
 }
 
 exports.binding = appWindow.generate();
 exports.onAppWindowClosed = onAppWindowClosed;
 exports.updateAppWindowProperties = updateAppWindowProperties;
 exports.appWindowShownForTests = onAppWindowShownForTests;