Bug 833628 - GStreamer backend has shutdown hang in content/media mochitests; r=cdouble
Fix stream length detection so that we don't report size=-1 to gst. Fixes issues
with qtdemux not liking unknown upstream byte size.
Bug 760140 - rework canPlayType in the GStreamer backend; r=cdouble
Bug 761018 - GStreamer video buffer handling optimization; r=cdouble