ServiceWorker: Add a new entry for LayoutTests into WATCHLISTS 


BUG=n/a
TEST=n/a
NOTRY=true

Review URL: https://codereview.chromium.org/378233004

git-svn-id: svn://svn.chromium.org/blink/trunk@177896 bbb929c8-8fbe-4397-9dbb-9b2b20218538