GitLab

This is a re-land of:
https://chromium-review.googlesource.com/c/chromium/src/+/2079134

The previous CL had a problem where a tracker may not being terminated.
This CL fixes that and tests are added.

PS#3 is the same as the original CL, so that the diffs can be easily
seen.

Bug: 1055844
Change-Id: I62cffba355980013db8fa392fbb66d0ea74749af
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2122242Reviewed-by: Robert Flack <flackr@chromium.org>
Commit-Queue: Xida Chen <xidachen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756018}