GitLab

- Prevent race condition in CastAudioOutputStream to prevent
FillNextBuffer() from calling AudioSourceCallback::OnMoreData() after
AudioOutputStream::Close() is called.
- FillNextBuffer() will now acquire running_lock_ for the entirety of
its scope.
- CastAudioOutputStream::Close() will synchronously block on
running_lock_ until FillNextBuffer() has completed before setting
running_ to false and continuing its close sequence.
- Subsequent calls to FillNextBuffer() will early return without calling
AudioSourceCallback::OnMoreData().
- Add infrastructure in CastAudioOutputStream unittests to pause and
resume the audio thread.
- Add a test in CastAudioOutputStream unittests to ensure that a call to
Close() will synchronously prevent any further callbacks.

mutex synchronization is removed, race condition is difficult to
reproduce in real-world testing.

Bug: 138695782
Test: Builds, unit tests pass, new unit test passes and fails when the
Change-Id: I11cdd64c0987298ba3fc6a9090359bd2715e6f03
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1761483Reviewed-by: Olga Sharonova <olka@chromium.org>
Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Commit-Queue: Hari Nandagopal <hnandagopal@google.com>
Cr-Commit-Position: refs/heads/master@{#691784}