[Media Router] Implement MediaRouterAction + MediaRouterUI tests.

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

Index: chrome/browser/ui/webui/media_router/media_router_dialog_controller.h
diff --git a/chrome/browser/ui/webui/media_router/media_router_dialog_controller.h b/chrome/browser/ui/webui/media_router/media_router_dialog_controller.h
index 96b1fe0f4db89523be31df8a0a1b0865cbb00af7..41bebbc882f4b011fea355b2f0d85962f6c452a2 100644
--- a/chrome/browser/ui/webui/media_router/media_router_dialog_controller.h
+++ b/chrome/browser/ui/webui/media_router/media_router_dialog_controller.h
@@ -21,6 +21,12 @@ class MediaRouterDialogController
  public:
   ~MediaRouterDialogController() override;
 
+  // Gets a reference to the MediaRouterDialogController associated with
+  // |web_contents|, creating one it does not exist. Returned value guaranteed

[Peter Kasting, 2015/06/04 00:17:53]

Nit: it -> if it

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

Done.

+  // 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.