service worker: Use TimeTicks to record event dispatch time

We can use base::TimeTicks in Blink now. Use it to record
service worker related event dispatching time so that we can
safely compare them with other timing like worker start time.

Cq-Include-Trybots: luci.chromium.try:linux_mojo
Bug: 877972
Change-Id: I399f9b7856e9ea2fdbbdc5c552149577cca3f09e
Reviewed-on: https://chromium-review.googlesource.com/1226473
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591969}
39 files changed