GitLab

The code assumes OnTaskCreated and OnTaskDestroyed are called in pairs
for the same task_id, soft fail if it's not the case.

Bug: 908308
Change-Id: I6d8bf5bdabbb601f53cf25e1d03edbc562613a84
Reviewed-on: https://chromium-review.googlesource.com/c/1351347Reviewed-by: Maajid <maajid@chromium.org>
Reviewed-by: Kazuhiro Inaba <kinaba@chromium.org>
Commit-Queue: Shao-Chuan Lee <shaochuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611073}