This is a reland of 92842b6a

Original change's description:
> [Fuchsia] Add WebEngineIntegrationTests.PlayVideo test
>
> Previously there were tests that play audio and tests that play video,
> but no tests were playing a file with both audio and video. Also video
> was not played to the end. Added PlayVideo test that plays
> bear-vp9-opus.webm to the end. Also updated SetBlockMediaLoading tests
> to share play_video.html and reduce amount of duplicated code.
>
> Bug: b/153914562
> Change-Id: Iba492ec252f692f7aa3f93c319d858a91bb38278
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2219404
> Auto-Submit: Sergey Ulanov <sergeyu@chromium.org>
> Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
> Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#773338}

TBR=kmarshall@chromium.org

Bug: b/153914562
Change-Id: I7f0c0d7040861d03dfd505c594eca1ccd0827ea3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2223260Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773763}