Increase GPU watchdog timeout limit on MacOSX from 10s to 15s

BUG=918490
TEST=bots
R=kbr@chromium.org

Change-Id: Icfb6e631090fe5a83a762bd45d32e550acb0e47e
Reviewed-on: https://chromium-review.googlesource.com/c/1416833
Commit-Queue: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623543}
1 file changed