service worker: Remove Install/Activate handling from the test helper.

Move them to the FakeServiceWorker for better separation of concerns.
Some of the affected tests were for non-S13nSW only, so those are
removed rather than updated since that codepath will be deleted soon.

Bug: 927651
Change-Id: I49c366be81f01e3589c6e29f4d62d406796a8af5
Reviewed-on: https://chromium-review.googlesource.com/c/1474957
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#633004}
6 files changed