Stop passing video encoding up front to WebmMuxer.

Instead of passing the video encoding on creation,
pass it on each frame instead. This enables the muxer
to be created before the encoding of the stream is known.

Bug: 1013590
Change-Id: If33ba3f7ac3633d2c3e9de16f0e027d6605006ff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1893853
Commit-Queue: Markus Handell <handellm@google.com>
Reviewed-by: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721043}
5 files changed