[MediaSession, Android] Adding visibility tests for MediaSession

content/browser/media/session/media_session.h

Index: content/browser/media/session/media_session.h
diff --git a/content/browser/media/session/media_session.h b/content/browser/media/session/media_session.h
index 2553c6d7885d58e9b1159201568cdb02d7f9256d..ce59d2e6aba340c4727a27f330882c7f0a7a9224 100644
--- a/content/browser/media/session/media_session.h
+++ b/content/browser/media/session/media_session.h
@@ -21,6 +21,7 @@ namespace content {
 
 class MediaSessionDelegate;
 class MediaSessionObserver;
+class MediaSessionVisibilityBrowserTestBase;
 
 // MediaSession manages the media session and audio focus for a given
 // WebContents. It is requesting the audio focus, pausing when requested by the
@@ -123,6 +124,7 @@ class MediaSession : public WebContentsObserver,
  private:
   friend class content::WebContentsUserData<MediaSession>;
   friend class ::MediaSessionBrowserTest;
+  friend class content::MediaSessionVisibilityBrowserTestBase;
 
   CONTENT_EXPORT void SetDelegateForTests(
       scoped_ptr<MediaSessionDelegate> delegate);