Implement MediaSession on top of the WebMediaPlayerDelegate.

content/common/frame_messages.h

Index: content/common/frame_messages.h
diff --git a/content/common/frame_messages.h b/content/common/frame_messages.h
index 1fd22bf592bbfd4f1ea34b9038a44f51b5a1e1d5..cf6fb54e2f8692117301a88cb9eba2da3a71fb1e 100644
--- a/content/common/frame_messages.h
+++ b/content/common/frame_messages.h
@@ -1266,16 +1266,6 @@ IPC_MESSAGE_ROUTED2(FrameHostMsg_SetSelectedColorInColorChooser,
                     int /* id */,
                     SkColor /* color */)
 
-// Notifies the browser that media has started/stopped playing.
-IPC_MESSAGE_ROUTED4(FrameHostMsg_MediaPlayingNotification,
-                    int64_t /* player_cookie, distinguishes instances */,
-                    bool /* has_video */,
-                    bool /* has_audio */,
-                    bool /* is_remote */)
-
-IPC_MESSAGE_ROUTED1(FrameHostMsg_MediaPausedNotification,
-                    int64_t /* player_cookie, distinguishes instances */)
-
 // Notify browser the theme color has been changed.
 IPC_MESSAGE_ROUTED1(FrameHostMsg_DidChangeThemeColor,
                     SkColor /* theme_color */)