[Media Router] Implement MediaRouterAction + MediaRouterUI tests.

chrome/browser/ui/toolbar/media_router_action.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_TOOLBAR_MEDIA_ROUTER_ACTION_H_
 #define CHROME_BROWSER_UI_TOOLBAR_MEDIA_ROUTER_ACTION_H_
 
 #include "chrome/browser/ui/toolbar/toolbar_action_view_controller.h"
 
+namespace media_router {
+class MediaRouterDialogController;
+}  // namespace media_router
+
 // The class for the Media Router component action that will be shown in
 // the toolbar.
 class MediaRouterAction : public ToolbarActionViewController {
  public:
   MediaRouterAction();
   ~MediaRouterAction() override;
 
   // ToolbarActionViewController implementation.
   const std::string& GetId() const override;
   void SetDelegate(ToolbarActionViewDelegate* delegate) override;
   gfx::Image GetIcon(content::WebContents* web_contents) override;
   gfx::ImageSkia GetIconWithBadge() override;
   base::string16 GetActionName() const override;
   base::string16 GetAccessibleName(content::WebContents* web_contents)
       const override;
   base::string16 GetTooltip(content::WebContents* web_contents)
       const override;
   bool IsEnabled(content::WebContents* web_contents) const override;
   bool WantsToRun(content::WebContents* web_contents) const override;
   bool HasPopup(content::WebContents* web_contents) const override;
   void HidePopup() override;
   gfx::NativeView GetPopupNativeView() override;
   ui::MenuModel* GetContextMenu() override;
   bool CanDrag() const override;
   bool ExecuteAction(bool by_user) override;
   void UpdateState() override;
 
  private:
+  // Returns a reference to the MediaRouterDialogController associated with
+  // |delegate_|'s current WebContents. Guaranteed to be non-null.
+  // |delegate_| and its current WebContents must not be null.
+  media_router::MediaRouterDialogController* GetMediaRouterDialogController();
+
   const std::string id_;
   const base::string16 name_;
 
   // Cached icons.
   gfx::Image media_router_idle_icon_;
 
   ToolbarActionViewDelegate* delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaRouterAction);
 };
 
 #endif  // CHROME_BROWSER_UI_TOOLBAR_MEDIA_ROUTER_ACTION_H_