Bug 1058418 - Make SBR::GetNextCachedData return a sane value, add more unimplemented function logging in MSE, drop unused mPrincipal from SBR.  r=cajbir
Bug 1059035 - Check IsAttached() before accessing mMediaSource in SourceBuffer::Remove.  r=cajbir
Bug 1044498 - Handle overlapped SourceBuffer appends by spinning up a new decoder.  Only implemented for WebM so far.  r=cajbir
Bug 1044498 - Save init segment for reuse during overlapped appends.  r=cajbir
Bug 1044498 - Fix a bunch of WebM buffered range bugs.  r=cajbir
Bug 1044498 - Return a null decoder when CreateSubDecoder is called in Shutdown state.  r=cajbir
Bug 1044498 - Improve calculation of init segment region.  r=cajbir
Bug 1044498 - Create new decoder if non-consecutive non-overlapped appended occurs.  r=cajbir
Bug 1059625 - Detach MediaSource upon decoder shutdown.  r=cajbir
Bug 1044498 - Pass saved init segment to decoder's NotifyDataAvailable.  r=cajbir