bug 1052266 - disable BlockingResourceBase spam
crash on vpx_codec_decode
silence UNIMP spam
Bug 1053657 - Apply minor Media Source Extension spec updates.
Bug 1059058 - Introduce abstraction to manager mapping between SourceBuffers and SourceBufferDecoders for the MediaSourceReader.
Bug 1062101 - Compute WebM frame duration from Δt of last frame.
bug 1062020 - forward discontinuity flag to MDSM