Transparent apps support

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.
 
 namespace app.window {
   dictionary CreateWindowOptions {
     // Id to identify the window. This will be used to remember the size
     // and position of the window and restore that geometry when a window
     // with the same id (and no explicit size or position) is later opened.
     DOMString? id;
@@ skipping 31 matching lines @@
 
     // Minimum height of the window.
     long? minHeight;
 
     // Maximum width of the window.
     long? maxWidth;
 
     // Maximum height of the window.
     long? maxHeight;
 
-    // Window type: 
+    // Window type:
     //  'shell' - the default window type
     //  'panel' - a panel, managed by the OS (Currently experimental, Ash only)
     [nodoc] DOMString? type;
 
     // Frame type: 'none' or 'chrome' (defaults to 'chrome').
     DOMString? frame;
 
     // Size of the content in the window (excluding the titlebar). If specified
     // in addition to any of the left/top/width/height parameters, this field
     // takes precedence. If a frameBounds is specified, the frameBounds take
     // precedence.
     Bounds? bounds;
 
+    // Enable window background transparency.
+    // Only supported in ash. Requires experimental API permission.
+    boolean? transparentBackground;
+
     // 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;
 
     // By default if you specify an id for the window, the window will only be
     // created if another window with the same id doesn't already exist. If a
     // window with the same id already exists that window is activated instead.
     // If you do want to create multiple windows with the same id, you can
     // set this property to false.
     boolean? singleton;
@@ skipping 93 matching lines @@
                        optional CreateWindowCallback callback);
 
     // Returns an $ref:AppWindow object for the
     // current script context (ie JavaScript 'window' object). This can also be
     // called on a handle to a script context for another page, for example:
     // otherWindow.chrome.app.window.current().
     [nocompile] static AppWindow current();
     [nocompile, nodoc] static void initializeAppWindow(object state);
   };
 };