Add tests for CORS, CSP, Mixed Content and canvas tainting of ServiceWorker's response.

CORS tests may change after the discussion in
https://github.com/slightlyoff/ServiceWorker/issues/347.


BUG=373120

Review URL: https://codereview.chromium.org/419783002

git-svn-id: svn://svn.chromium.org/blink/trunk@179595 bbb929c8-8fbe-4397-9dbb-9b2b20218538