ServiceWorker: Add test for navigator.serviceWorker.active


BUG=379012
TEST=run_webkit_tests.py http/tests/serviceworker/{installing,waiting,active}.html

Review URL: https://codereview.chromium.org/373013002

git-svn-id: svn://svn.chromium.org/blink/trunk@178319 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Auto-rebaseline for r178305

http://src.chromium.org/viewvc/blink?view=revision&revision=178305

BUG=390587
TBR=wangxianzhu@chromium.org

Review URL: https://codereview.chromium.org/402523002

git-svn-id: svn://svn.chromium.org/blink/trunk@178320 bbb929c8-8fbe-4397-9dbb-9b2b20218538