3a44bbda74
Benchmarks were failing because the code was reading the `frameCount` and `repetitionCount` before reading any frames out of the codec. The codec gets implicitly initialized when you read a frame, but we should return it to the user initialized so that `frameCount` and `repetitionCount` work even if you haven't read a frame yet. This is consistent with how CanvasKit's codec works. Also, modified our unit tests so that they exercise the codecs in this way.