GitLab

Canonical fix:
- Model liveness through PannerNode (AudioNode), i.e., keep alive
  listener from there.
- Change off-thread handler to use a weak root

This works as AudioNode disposes the handler in the pre-finalizer.

Bug: 928781, 843903
Change-Id: I3b7454adcfbd2ab2c993974c3cda0415c1a20427
Reviewed-on: https://chromium-review.googlesource.com/c/1486092Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635139}