Allow GPU watchdog to keep waiting for acknowledgement

if we know one is already issued by the monitored thread.

This is done through a finch experiment, so we can see if how this
strategy affects GPU crashes.

BUG=885066
TEST=compile
R=piman@chromium.org

Change-Id: I51289c3bd4cc27d0361e3cda6742cdb62b4e0116
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1582976
Reviewed-by: Antoine Labour <piman@chromium.org>
Commit-Queue: Zhenyao Mo <zmo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654225}
3 files changed