chrome/browser: Add flag to chrome://flags to enable ChromeosVideoDecoder.

This CL adds a flag to chrome://flags to manually enable/disable the
ChromeosVideoDecoder feature. This Feature enables the new
media::VideoDecoder-based video decoders on ChromeOS.

TEST=enabled/disabled flag in Chrome on nocture, and verified logs

BUG=None

Change-Id: I5df33207f7f2081260a66c8406fc0dceed7a0cc4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1997431
Commit-Queue: David Staessens <[email protected]>
Reviewed-by: Miguel Casas <[email protected]>
Reviewed-by: Alexandre Courbot <[email protected]>
Cr-Commit-Position: refs/heads/master@{#732709}
5 files changed