I'm not sure where the definition for mediaControlsUserAgentStyleSheet is, but it's causing compile errors with GStreamer on Windows since http://trac.webkit.org/changeset/156546 I assume it's part of CA. This makes it compile, but I have no idea what this code is doing.
Created attachment 217836 [details] Patch
Comment on attachment 217836 [details] Patch CA is the wrong protector. This should be #if ENABLE(MEDIA_CONTROLS_SCRIPT).
Created attachment 219388 [details] Patch
Are you sure this shouldn't be #if ENABLE(VIDEO_TRACK) ?
Created attachment 219391 [details] Patch
This isn't causing me a problem anymore because I'm only compiling this code with MEDIA_CONTROLS_SCRIPT and VIDEO_TRACK enabled.