Add app.window.alphaEnabled() and onAlphaEnabledChanged.

chrome/common/extensions/api/app_window.idl

 // 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.
 
 // Use the <code>chrome.app.window</code> API to create windows. Windows
 // have an optional frame with title bar and size controls. They are not
 // associated with any Chrome browser windows. See the <a
 // href="https://github.com/GoogleChrome/chrome-app-samples/tree/master/window-state">
 // Window State Sample</a> for a demonstration of these options.
 namespace app.window {
@@ skipping 333 matching lines @@
     // Accessors for testing.
     [nodoc] boolean hasFrameColor;
     [nodoc] long activeFrameColor;
     [nodoc] long inactiveFrameColor;
     [nodoc] boolean? firstShowHasHappened;
 
     // Set whether the window should stay above most other windows. Requires the
     // <code>"alwaysOnTopWindows"</code> permission.
     static void setAlwaysOnTop(boolean alwaysOnTop);
 
+    // Can the window use alpha transparency?
+    // TODO(jackhou): Document this properly before going to stable.
+    [nodoc] static boolean alphaEnabled();
+
     // The JavaScript 'window' object for the created child.
     [instanceOf=Window] object contentWindow;
 
     // The id the window was created with.
     DOMString id;
 
     // The position, size and constraints of the window's content, which does
     // not include window decorations.
     // This property is new in Chrome 36.
     Bounds innerBounds;
@@ skipping 62 matching lines @@
 
     // Fired when the window is maximized.
     [nocompile] static void onMaximized();
 
     // Fired when the window is minimized.
     [nocompile] static void onMinimized();
 
     // Fired when the window is restored from being minimized or maximized.
     [nocompile] static void onRestored();
 
+    // Fired when the window's ability to use alpha transparency changes.
+    [nocompile, nodoc] static void onAlphaEnabledChanged();
+
     // Event for testing. Lets tests wait until a window has been shown.
     [nocompile, nodoc] static void onWindowFirstShown();
   };
 };