GitLab

The test was mocking time only partially: the window.performance.now()
should be mocked as well.

BUG=610464
TBR=dgozman

Change-Id: If9c81662235e43ee2ffafef2ed772158f3a74968
Reviewed-on: https://chromium-review.googlesource.com/828443Reviewed-by: Andrey Lushnikov <lushnikov@chromium.org>
Commit-Queue: Andrey Lushnikov <lushnikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524327}