NOT FOR LANDING Introduce and use WebMediaSession

public/web/WebFrameClient.h

Index: public/web/WebFrameClient.h
diff --git a/public/web/WebFrameClient.h b/public/web/WebFrameClient.h
index ce2106a8a91a53befc6f9927e1d9ba20a6508cde..f0859bbfdc75075b9c1649c61dbfae20b2421f9b 100644
--- a/public/web/WebFrameClient.h
+++ b/public/web/WebFrameClient.h
@@ -75,6 +75,7 @@ class WebGeolocationClient;
 class WebMediaPlayer;
 class WebMediaPlayerClient;
 class WebMediaPlayerEncryptedMediaClient;
+class WebMediaSession;
 class WebMIDIClient;
 class WebNotificationPermissionCallback;
 class WebPermissionClient;
@@ -117,6 +118,9 @@ public:
     virtual WebMediaPlayer* createMediaPlayer(WebLocalFrame*, const WebURL&, WebMediaPlayerClient*, WebMediaPlayerEncryptedMediaClient*, WebContentDecryptionModule*) { return 0; }
 
     // May return null.
+    virtual WebMediaSession* createMediaSession(WebLocalFrame*) { return 0; }
+
+    // May return null.
     virtual WebApplicationCacheHost* createApplicationCacheHost(WebLocalFrame*, WebApplicationCacheHostClient*) { return 0; }
 
     // May return null.