[Media Router] Implement MediaRouterAction + MediaRouterUI tests.

chrome/browser/ui/toolbar/media_router_action.h

Index: chrome/browser/ui/toolbar/media_router_action.h
diff --git a/chrome/browser/ui/toolbar/media_router_action.h b/chrome/browser/ui/toolbar/media_router_action.h
index da2bc24c089ecd817800d93b73b2c45dd71ffbb7..a3fe56bd8429cd04bb727bf79fcaaf7326dd1d8d 100644
--- a/chrome/browser/ui/toolbar/media_router_action.h
+++ b/chrome/browser/ui/toolbar/media_router_action.h
@@ -35,6 +35,8 @@ class MediaRouterAction : public ToolbarActionViewController {
   void UpdateState() override;
 
  private:
+  content::WebContents* GetMediaRouterDialog() const;

[Peter Kasting, 2015/06/04 00:17:52]

Const functions may not return non-const pointers.  Return a const pointer, or
if that's impossible make the function non-const.

[imcheng (use chromium acct), 2015/06/04 01:04:20]

Removed this function since it is not used.

+
   const std::string id_;
   const base::string16 name_;