Revert of Add lock to fix race in AudioRendererMixerInput. (patchset #5 id:80001 of https://codereview.chromium.org/1748183006/ )

Reason for revert:
This seems to cause failures in LayoutTests/http/tests/security/media. Not sure why this wasn't caught by CQ...

Tracking CQ weirdness here:
https://bugs.chromium.org/p/chromium/issues/detail?id=592079

Original issue's description:
> Add lock to fix race in AudioRendererMixerInput.
>
> Clusterfuzz identified a race between the media thread calling SetVolume
> and the audio device thread calling ProvideInput. Add a lock to
> synchronize access to |volume_| between threads.
>
> Also adds some thread_checkers to just firm up the contract that the
> majority of these methods are called only by the media thread.
>
> BUG=588992
>
> Committed: https://crrev.com/57c6958a99f2c62a4408d2a9d262a22129309106
> Cr-Commit-Position: refs/heads/master@{#379349}

TBR=dalecurtis@chromium.org,olka@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=588992

Review URL: https://codereview.chromium.org/1771463002

Cr-Commit-Position: refs/heads/master@{#379388}

0 files changed, 0 insertions, 0 deletions