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 @@
     // Maximum width of the window.
     long? maxWidth;
 
     // Maximum height of the window.
     long? maxHeight;
 
     // Window type: 'shell' (the default) is the only currently supported value.
     DOMString? type;
 
     // Frame type: 'none' or 'chrome' (defaults to 'chrome').
+    // Requires experimental API permission.

[reveman, 2012/10/11 17:25:58]

It's only 'experimental-html' frame type that is experimental, right? Please
update the comment so it doesn't seem like all frame types are experimental
before landing.

[Bernie, 2012/11/08 01:55:13]

Done.

     DOMString? frame;
+
+    // Enable window background transparency.
+    // Only supported in ash. Requires experimental API permission.
+    boolean? transparentBackground;
   };
 
   callback CreateWindowCallback =
       void ([instanceOf=AppWindow] object created_window);
 
   dictionary AppWindow {
     // Focus the window.
     static void focus();
 
     // Minimize the window.
@@ skipping 42 matching lines @@
     // If you specify both a regular and a default value for the same option
     // the regular value is the only one that takes effect.
     static void create(DOMString url,
                        optional CreateWindowOptions options,
                        optional CreateWindowCallback callback);
 
     [nocompile] static AppWindow current();
     [nocompile, nodoc] static void initializeAppWindow(object state);
   };
 };