GitLab

- Extends RendererConfig to handle VideoDecoders.
- Extends the MOJO interfaces for DemuxerStreams with VIDEO.
- Adds the VideoFrame type plus converters to media types.
- Extends DemuxerStreamProviderShim to handle multiple streams.

BUG=410451
TEST=YouTube videos play with MOJO renderer!

Review URL: https://codereview.chromium.org/684963003

Cr-Commit-Position: refs/heads/master@{#302728}