Under some circumstances, and seen on Windows 8, a decoded sample can be returned without the MFT returning MF_E_TRANSFORM_STREAM_CHANGE.
For historical reasons, we required that message to be returned at least once to set the output image size. This was required as the decoder used to be recycled with different video streams.
This is no longer the case, we can rely on the video info instead. It also greatly simplifies the code
MozReview-Commit-ID: H14KBiNWrjQ
c48398abd9