Handle the Cast.Platform.VideoResolution metric in the non-CMA renderer.

This is part of the productionization process of the non-CMA starboard
renderer.

This change also adds safeguards against codecs changing mid-stream,
since that is not supported by starboard (or cast in general, as far as
I know).

Bug: b:428268070
Change-Id: I59a4837eeea2403174f376c129deafc217176e0c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6799133
Reviewed-by: Shawn Quereshi <shawnq@google.com>
Commit-Queue: Antonio Rivera <antoniori@google.com>
Cr-Commit-Position: refs/heads/main@{#1504212}