GitLab

to avoid a race with rendering callback (https://cs.chromium.org/chromium/src/media/audio/pulse/pulse_output.cc?sq=package:chromium&rcl=1475536681&l=148)

BUG=285242

Review-Url: https://codereview.chromium.org/2394483002
Cr-Commit-Position: refs/heads/master@{#422845}