Bug 830734 - Implement Path primitives. r=roc
Bug 830734 - Add tests for path object in canvas. r=roc
Bug 907162 - Fix MediaDecoderStateMachine might dispatch MediaDecoder::PlaybackEnded more than once and trigger multiple 'ended' events in HTMLMediaElement. r=cpearce
Bug 982075 - Make addEntriesToListFile() in buildlist.py deterministic. r=ted
Bug 983207 - Tracks created through a TrackElement should have a default mode of 'disabled'. r=cpearce

- I've refactored the way we set modes as well, making it a part
of the TextTrack ctors.
- I've also changed TextTracks in the track tests to have their
mode set to 'hidden' in order to be able to call TextTrack::Cues.
This is correct since TextTracks with a mode of 'disabled' do not
return null for their cue lists.