Add support for transparent background API

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.
 namespace app.window {
 
   // Previously named Bounds.
@@ skipping 203 matching lines @@
     // to disable this style on nested elements.<br>
     // Use of <code>FrameOptions</code> is only supported in dev channel.
     (DOMString or FrameOptions)? frame;
 
     // Size and position of the content in the window (excluding the titlebar).
     // If an id is also specified and a window with a matching id has been shown
     // before, the remembered bounds of the window will be used instead.
     [deprecated="Use innerBounds or outerBounds."] ContentBounds? bounds;
 
     // Enable window background transparency.
-    // Only supported in ash. Requires experimental API permission.
-    boolean? transparentBackground;
+    // Only supported in ash. Requires app.window.alpha API permission.
+    boolean? alphaEnabled;
 
     // The initial state of the window, allowing it to be created already
     // fullscreen, maximized, or minimized. Defaults to 'normal'.
     State? state;
 
     // If true, the window will be created in a hidden state. Call show() on
     // the window to show it once it has been created. Defaults to false.
     boolean? hidden;
 
     // If true, the window will be resizable by the user. Defaults to true.
@@ skipping 105 matching lines @@
 
     // Accessors for testing.
     [nodoc] boolean hasFrameColor;
     [nodoc] long activeFrameColor;
     [nodoc] long inactiveFrameColor;
 
     // Set whether the window should stay above most other windows. Requires the
     // <code>"alwaysOnTopWindows"</code> permission.
     static void setAlwaysOnTop(boolean alwaysOnTop);
 
+    // Does the window allow a transparent background?
+    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 49 matching lines @@
   interface Events {
     // Fired when the window is resized.
     [nocompile] static void onBoundsChanged();
 
     // Fired when the window is closed.
     [nocompile] static void onClosed();
 
     // Fired when the window is fullscreened.
     [nocompile] static void onFullscreened();
 
+    // Fired when the alphaEnabled flag changes.
+    [nocompile] static void onAlphaEnabledChanged();
+
     // 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();
   };
 };