ServiceWorker: Add force-refreshed page registration layout test.

Add registration test for an iframe reloaded bypassing the cache.
The registration should succeed in this case.

BUG=392405

Review URL: https://codereview.chromium.org/412733003

git-svn-id: svn://svn.chromium.org/blink/trunk@178920 bbb929c8-8fbe-4397-9dbb-9b2b20218538