While encoder parameters for lossless encoding are set correctly,
output is not lossless due to pixel format being set to
`AV_PIX_FMT_YUV420P` which is inherently lossy due to chroma subsampling.
This was reported in T61569 and was merged to T57397, but there were
2 bugs - one for encoding and one for decoding.
Set pixel format to `AV_PIX_FMT_YUV444P` when rendering lossless H264
files. This format isn't available in `codec->pix_fmts[0]` and it looks,
that it has to be hard-coded.
Reviewed By: sergey
Differential Revision: D11458
0ea0ccc4ff