[M155] [Tab Share Protection] Deliver a black frame when capture is paused

Original change's description:
> [Tab Share Protection] Deliver a black frame when capture is paused
>
> Pausing a video source pushes one black frame to the consumer so that it
> stops showing whatever the source was displaying. The frame was built by
> media::VideoFrame::CreateBlackFrame(), which stamps it with a
> default-constructed capture version. That compares equal to the track's
> initial watermark, so it works right up until something raises the
> watermark -- in practice a source change, which bumps
> capture_version_source in
> MediaStreamVideoCapturerSource::ChangeSourceImpl. From that point
> MediaStreamVideoTrack discards every black frame as kOldCaptureVersion
> and the consumer keeps rendering the last real frame. A tab paused by
> enterprise tab sharing protection therefore kept showing protected
> content to the remote peer, but only once the user had switched shared
> surfaces at least once, which is why the failure looked intermittent.
> * Add VideoTrackAdapter::DeliverBlackFrameOnVideoTaskRunner, which builds
>   the frame on the video task runner and stamps it with the source's
>   current capture version and a timestamp that continues the source's
>   timeline. The advance is deliberately past kMaxTimeBetweenFrames: a
>   merely monotonic delta is discarded as
>   kResolutionAdapterFrameRateIsHigherThanRequested whenever the source
>   has a max frame rate, which is the norm for screen share.
> * In MediaStreamVideoSource::StopForRestart, post the frame size and the
>   capture version to that method instead of a pre-built frame.
> * In UserMediaProcessor::OnDeviceRequestStateChange, bail out unless the
>   source is a video source. The browser sends this notification once per
>   device sharing the DesktopMediaID, so with tab audio it also arrives
>   for the audio source, and a static_cast of a non-null pointer is never
>   null, so the existing null check could not catch it. Also skip the
>   restart when the source has no current format.
> * Add VideoTrackAdapterFixtureTest.BlackFrameIsDeliveredAndStamped and
>   MediaStreamVideoSourceTest.StopForRestartDeliversBlackFrameToSink.
>
> TAG=agy
> CONV=71d2c3c2-20a2-42dd-a7df-c2e37f4bf62f
>
> Bug: 563063637
> Change-Id: I56f7017860eb525b6b986b10dcfb0f0a36a686e2
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/8414448
> Auto-Submit: Nasser Al-shawwa <alshawwa@chromium.org>
> Reviewed-by: Guido Urdaneta <guidou@chromium.org>
> Commit-Queue: Guido Urdaneta <guidou@chromium.org>
> Reviewed-by: Jordan Bayles <jophba@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1700650}

(cherry picked from commit f1dce53dc3f97d825e6ac95f0b010fafa058c5df)

Bug: 563481114,563063637
Change-Id: I56f7017860eb525b6b986b10dcfb0f0a36a686e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/8427543
Bot-Commit: rubber-stamper@appspot.gserviceaccount.com <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: chrome-cherry-picker@chops-service-accounts.iam.gserviceaccount.com <chrome-cherry-picker@chops-service-accounts.iam.gserviceaccount.com>
Commit-Queue: rubber-stamper@appspot.gserviceaccount.com <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Nasser Al-shawwa <alshawwa@chromium.org>
Cr-Commit-Position: refs/branch-heads/8059@{#409}
Cr-Branched-From: 199ac2cd7ab289e11c2236bd2cede848781213da-refs/heads/main@{#1697595}