[ServiceWorker] Tests for Cache

These tests exercise the following methods on Cache objects:
* add
* addAll
* put
* match
* matchAll

BUG=374802

Review URL: https://codereview.chromium.org/425413002

git-svn-id: svn://svn.chromium.org/blink/trunk@184242 bbb929c8-8fbe-4397-9dbb-9b2b20218538