ServiceWorker: Strip fragment identifier from scope and script URLs

Since the fragment is not sent to the server, it can't be matched
by the scope anyway.

BUG=375422

Review URL: https://codereview.chromium.org/291263002

git-svn-id: svn://svn.chromium.org/blink/trunk@174610 bbb929c8-8fbe-4397-9dbb-9b2b20218538