Avoid hitting the thread check when WebRtcAudioRenderer is going away.

We need to reset the render_thread_checker and render_converter_ when the WebRtcAudioRenderer is going away.

NOTRY=true

BUG=264611
TEST=manual test webrtc with --enable-audio-track-processor

Review URL: https://codereview.chromium.org/178153007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255158 0039d316-1c4b-4281-b951-d872f2087c98
[Android] Fix compilation error: unused variable 'kAllowedToAccessOnNonjoinableThread'

While building with clang=1, clang reports this error about the above variable being unused.

BUG=349521
NOTRY=true

Review URL: https://codereview.chromium.org/188003002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255159 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255159