Bug 855130 - Implement HTMLVideoElement's VideoPlaybackQuality (from

 Media Source Extensions specification).  r=roc
Bug 855130 - Implement a minimal working subset of the Media Source

 Extensions specification.  r=roc
Bug 855130 - Implement URL::createObjectURL overload for

 MediaSources.  Add MediaSources to HostObjectProtocolHandler.  Make
 MediaSource a real interface.  r=khuey
Bug 855130 - Integrate MediaSource into HTMLMediaElement.  r=roc
Bug 855130 - Add initial tests for Media Source Extensions.  r=roc
Bug 855130 - Clobber build.