MozReview-Commit-ID: LxZtvFpg3mD --HG-- extra : rebase_source : 5f3c9132a386b1d290b8c0b169011baec4240b34 extra : source : b30985c8d5b99f6770d156942e5f91a0a408513a
1. extract MediaDecoder::Statistics to its own file. 2. sort out include orders of MediaDecoderStateMachine.cpp