GitLab

Fixes a missing lock acquisition from the listener thread when
accessing |channel_|.

Also removes the TSAN suppression for this bug.

BUG=628481
TBR=glider@chromium.org for suppression removal

Review-Url: https://codereview.chromium.org/2158893002
Cr-Commit-Position: refs/heads/master@{#406033}