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 0f7581069e62907f4952a9b50cf6526bca494aeb..c00c1cd980be0705b64ffb021e60b8a2e917df40 100644
--- a/public/web/WebFrameClient.h
+++ b/public/web/WebFrameClient.h
@@ -74,6 +74,7 @@ class WebGeolocationClient;
 class WebMediaPlayer;
 class WebMediaPlayerClient;
 class WebMediaPlayerEncryptedMediaClient;
+class WebMediaSession;
 class WebMIDIClient;
 class WebNotificationPermissionCallback;
 class WebPermissionClient;
@@ -109,7 +110,11 @@ public:
 
     // May return null.
     // WebContentDecryptionModule* may be null if one has not yet been set.
-    virtual WebMediaPlayer* createMediaPlayer(WebLocalFrame*, const WebURL&, WebMediaPlayerClient*, WebMediaPlayerEncryptedMediaClient*, WebContentDecryptionModule*) { return 0; }
+    // WebMediaSession* may be null if the player should be part of the default media session.
+    virtual WebMediaPlayer* createMediaPlayer(WebLocalFrame*, const WebURL&, WebMediaPlayerClient*, WebMediaPlayerEncryptedMediaClient*, WebContentDecryptionModule*, WebMediaSession*) { return 0; }
+
+    // May return null.
+    virtual WebMediaSession* createMediaSession(WebLocalFrame*) { return 0; }
 
     // May return null.
     virtual WebApplicationCacheHost* createApplicationCacheHost(WebLocalFrame*, WebApplicationCacheHostClient*) { return 0; }