Upstream service wrkr "skipWaiting" tests to WPT

**skip-waiting-installed**

This test exists in both the Web Platform Tests project and in the
Chromium project, but the two versions differ slightly. Update the Web
Platform Tests version with improvements available in the Chromium
version:

- Remove unnecessary `<script>` include
- Discourage worker termination by invoking `event.waitUntil`
- Refactor promise management to avoid timing out in response to
  assertion failures
- Introduce a "use strict" directive

The Chromium version contains an additional assertion that is faulty.
Extend the Web Platform Tests version with a corrected form of this
assertion. Persist the Chromium version in its current state in order to
preserve test coverage, but annotate that version with references to a
new Chromium issue which tracks the resolution of the underlying bug.

**skip-waiting-using-registration**

This test exists in equivalent forms in both the Web Platform Tests
project and in the Chromium project. Update the Web Platform Tests
version:

- Remove unnecessary `<script>` include
- Refactor promise management to avoid timing out in response to
  assertion failures
- Increase prevision of test "cleanup" logic
- Introduce a "use strict" directive

Remove the Chromium version of the test.

**skip-waiting-without-client**

This test exists in equivalent forms in both the Web Platform Tests
project and in the Chromium project. Remove an unnecessary `<script>`
include from the Web Platform Tests version. Remove the Chromium version
of the test.

**skip-waiting-without-using-registration**

This test exists in equivalent forms in both the Web Platform Tests
project and in the Chromium project. Update the Web Platform Tests
version:

- Remove unnecessary `<script>` include
- Increase prevision of test "cleanup" logic
- Introduce a "use strict" directive

Remove the Chromium version of the test.

**skip-waiting**

This test exists in equivalent forms in both the Web Platform Tests
project and in the Chromium project. Update the Web Platform Tests
version:

- Remove unnecessary `<script>` include
- Increase prevision of test "cleanup" logic
- Introduce a "use strict" directive

Remove the Chromium version of the test.

---

Remove the `skip-waiting-worker.js` "resource" file from the Chromium
project as it is no longer referenced by any tests.

BUG=688116, 725616
R=falken@chromium.org

Review-Url: https://codereview.chromium.org/2900183002
Cr-Commit-Position: refs/heads/master@{#475361}
14 files changed