[Media Router] Implement MediaRouterAction + MediaRouterUI tests.

chrome/browser/ui/webui/media_router/media_router_dialog_controller.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_H_
 #define CHROME_BROWSER_UI_WEBUI_MEDIA_ROUTER_MEDIA_ROUTER_DIALOG_CONTROLLER_H_
 
 #include "base/macros.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
 namespace media_router {
 
 // An instance of this class is tied to a WebContents known as the initiator,
 // and is lazily created when a Media Router dialog needs to be shown.
 // The MediaRouterDialogController allows creating, querying, and removing a
 // Media Router dialog modal to the initiator WebContents.
 // This class is not thread safe and must be called on the UI thread.
 class MediaRouterDialogController
     : public content::WebContentsUserData<MediaRouterDialogController> {
  public:
   ~MediaRouterDialogController() override;
 
+  // Gets a reference to the MediaRouterDialogController associated with
+  // |web_contents|, creating one if it does not exist. The returned pointer is
+  // guaranteed to be non-null.
+  static MediaRouterDialogController* GetOrCreateForWebContents(
+      content::WebContents* web_contents);
+
   // Shows the media router dialog modal to the initiator WebContents.
   // Creates the dialog if it did not exist prior to this call.
   // If the dialog already exists, brings the dialog to the front.
   // Returns WebContents for the media router dialog.
   content::WebContents* ShowMediaRouterDialog();
 
   // Returns the media router dialog WebContents.
   // Returns nullptr if there is no dialog.
   content::WebContents* GetMediaRouterDialog() const;
 
@@ skipping 30 matching lines @@
   bool media_router_dialog_pending_;
 
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaRouterDialogController);
 };
 
 }  // namespace media_router
 
 #endif  // CHROME_BROWSER_UI_WEBUI_MEDIA_ROUTER_MEDIA_ROUTER_DIALOG_CONTROLLER_H_