Add always-on-top property to app windows

chrome/common/extensions/api/app_window.idl

Index: chrome/common/extensions/api/app_window.idl
diff --git a/chrome/common/extensions/api/app_window.idl b/chrome/common/extensions/api/app_window.idl
index 032897408f648ca375fff7d834cd4e5dd7686595..65f34f853cb615a80bfe16a6ea0cf52301429073 100644
--- a/chrome/common/extensions/api/app_window.idl
+++ b/chrome/common/extensions/api/app_window.idl
@@ -103,6 +103,13 @@ namespace app.window {
     // If you do want to create multiple windows with the same id, you can
     // set this property to false.
     boolean? singleton;
+
+    // If true, the window will stay above most other windows. If there are
+    // multiple windows of this kind, the currently focused window will be in
+    // the foreground. Defaults to false. Call <code>setAlwaysOnTop()</code> on
+    // the window to change this property after creation.
+    // Currently available in the Dev channel only.
+    boolean? alwaysOnTop;
   };
 
   // Called in the creating window (parent) before the load event is called in
@@ -172,6 +179,14 @@ namespace app.window {
     // TODO(stevenjb): Investigate implementing this on Windows and OSX.
     [nodoc] static void setIcon(DOMString icon_url);
 
+    // Is the window always on top?
+    // Currently available in the Dev channel only.
+    static boolean isAlwaysOnTop();
+
+    // Set whether the window should stay above most other windows.
+    // Currently available in the Dev channel only.
+    static void setAlwaysOnTop(boolean always_on_top);
+
     // The JavaScript 'window' object for the created child.
     [instanceOf=Window] object contentWindow;
   };