ServiceWorker: Remove navigator.serviceWorker.{installing,waiting,active} (Blink)

These attributes are gone:
https://slightlyoff.github.io/ServiceWorker/spec/service_worker/index.html#service-worker-container

Chromium: https://codereview.chromium.org/544023002/


BUG=404982
TEST=run_webkit_tests.py --debug http/tests/serviceworker/

Review URL: https://codereview.chromium.org/541943003

git-svn-id: svn://svn.chromium.org/blink/trunk@181534 bbb929c8-8fbe-4397-9dbb-9b2b20218538