Add always-on-top property to app windows

apps/shell_window.h

 // Copyright 2013 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.
 
 #ifndef APPS_SHELL_WINDOW_H_
 #define APPS_SHELL_WINDOW_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/extensions/extension_icon_image.h"
@@ skipping 105 matching lines @@
     ui::WindowShowState state;
 
     // If true, don't show the window after creation.
     bool hidden;
 
     // If true, the window will be resizable by the user. Defaults to true.
     bool resizable;
 
     // If true, the window will be focused on creation. Defaults to true.
     bool focused;
+
+    // If true, the window will stay on top of other windows that are not
+    // configured to be always on top. Defaults to false.
+    bool always_on_top;
   };
 
   class Delegate {
    public:
     virtual ~Delegate();
 
     // General initialization.
     virtual void InitWebContents(content::WebContents* web_contents) = 0;
     virtual NativeAppWindow* CreateNativeAppWindow(
         ShellWindow* window,
@@ skipping 245 matching lines @@
 
   // The window content is visible.
   bool is_content_visible_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellWindow);
 };
 
 }  // namespace apps
 
 #endif  // APPS_SHELL_WINDOW_H_