Add test for ServiceWorkerRegistration's attributes after register is called

This wasn't systemically tested before. Some tests partially covered it,
which clouds those tests' purpose and makes it unclear what the total
coverage of ServiceWorkerRegistration is.

BUG=396400

Review URL: https://codereview.chromium.org/487203002

git-svn-id: svn://svn.chromium.org/blink/trunk@180619 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Service Worker: Don't let tests register in the default scope

Tests should use unique scopes so they don't interfere with each other.
The default scope is particularly dangerous because it means
layout tests themselves are controlled by the worker, if the test failed
to unregister.

This patch fixes a test that used the default scope and changes our
convenience function to not allow default scope.

Review URL: https://codereview.chromium.org/487773002

git-svn-id: svn://svn.chromium.org/blink/trunk@180620 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Auto-rebaseline for r180610

http://src.chromium.org/viewvc/blink?view=revision&revision=180610

BUG=388780,392759
TBR=zhaoze.zhou@partner.samsung.com

Review URL: https://codereview.chromium.org/477913006

git-svn-id: svn://svn.chromium.org/blink/trunk@180621 bbb929c8-8fbe-4397-9dbb-9b2b20218538