Show Media Router toolbar icon ephemerally for MR dialogs

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

Index: chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl.h
diff --git a/chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl.h b/chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl.h
index 1c19a127c3a7735939edf9aeae931cdd539b64c1..1d21c0886b9e3e91013825a2d01aa7c0762fc7dd 100644
--- a/chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl.h
+++ b/chrome/browser/ui/webui/media_router/media_router_dialog_controller_impl.h
@@ -15,6 +15,7 @@
 FORWARD_DECLARE_TEST(MediaRouterActionUnitTest, IconPressedState);
 
 class MediaRouterAction;
+class MediaRouterActionController;
 
 namespace media_router {
 
@@ -41,6 +42,8 @@ class MediaRouterDialogControllerImpl :
 
   void UpdateMaxDialogSize();
 
+  MediaRouterAction* action() { return action_.get(); }
+
  private:
   class DialogWebContentsObserver;
   friend class content::WebContentsUserData<MediaRouterDialogControllerImpl>;
@@ -75,6 +78,10 @@ class MediaRouterDialogControllerImpl :
   // when the overflow menu is opened and destroyed when the menu is closed.
   base::WeakPtr<MediaRouterAction> action_;
 
+  // |action_controller_| is responsible for showing and hiding the toolbar
+  // action. It's owned by MediaRouterUIService, which outlives |this|.
+  MediaRouterActionController* action_controller_;
+
   base::WeakPtrFactory<MediaRouterDialogControllerImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaRouterDialogControllerImpl);