Move Singleton and related structs to namespace base

chromecast/media/base/media_message_loop.h

Index: chromecast/media/base/media_message_loop.h
diff --git a/chromecast/media/base/media_message_loop.h b/chromecast/media/base/media_message_loop.h
index e9f1e09abc295289f6ab40e31663cf50b3d3b8d7..c52e4df26196b7b64b1e395f075566cc23acd4a2 100644
--- a/chromecast/media/base/media_message_loop.h
+++ b/chromecast/media/base/media_message_loop.h
@@ -21,12 +21,11 @@ class MediaMessageLoop {
  public:
   static scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner();
 
- private:
-  friend struct DefaultSingletonTraits<MediaMessageLoop>;
-  friend class Singleton<MediaMessageLoop>;
-
   static MediaMessageLoop* GetInstance();
 
+ private:
+  friend struct base::DefaultSingletonTraits<MediaMessageLoop>;
+
   MediaMessageLoop();
   ~MediaMessageLoop();