[Media Router] Only keep track of toolbar MediaRouterAction in MediaRouterDialogControllerImpl.

chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl.h

 // Copyright 2015 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 CHROME_BROWSER_UI_WEBUI_MEDIA_ROUTER_MEDIA_ROUTER_DIALOG_CONTROLLER_IMPL_H_
 #define CHROME_BROWSER_UI_WEBUI_MEDIA_ROUTER_MEDIA_ROUTER_DIALOG_CONTROLLER_IMPL_H_
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 46 matching lines @@
   void OnDialogNavigated(const content::LoadCommittedDetails& details);
 
   void PopulateDialog(content::WebContents* media_router_dialog);
 
   scoped_ptr<DialogWebContentsObserver> dialog_observer_;
 
   // True if the controller is waiting for a new media router dialog to be
   // created.
   bool media_router_dialog_pending_;
 
+  // |action_| refers to the MediaRouterAction on the toolbar, rather than
+  // overflow menu. A MediaRouterAction is always created for the toolbar
+  // first. Any subsequent creations for the overflow menu will not be set as
+  // |action_|.
+  // The lifetime of |action_| is dependent on the creation and destruction of
+  // a browser window. The overflow menu's MediaRouterAction is only created
+  // when the overflow menu is opened and destroyed when the menu is closed.
   base::WeakPtr<MediaRouterAction> action_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaRouterDialogControllerImpl);
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_UI_WEBUI_MEDIA_ROUTER_MEDIA_ROUTER_DIALOG_CONTROLLER_IMPL_H_