VideoTrackRecorder: add support for more codecs on construction

Small CL that moves the |use_vp9| ctor param to a CodecId.

This is a step in a series of CLs to add support for
H264 to MediaRecorder (see https://crrev.com/1886123002/)

BUG=600895

Review URL: https://codereview.chromium.org/1892673002

Cr-Commit-Position: refs/heads/master@{#387484}
4 files changed