Reland of "Introducing the WebServiceWorkerCache."

The original commit had to be reverted because of updates in V8
bindings for arrays.

TBR=jsbell@chromium.org,jkarlin@chromium.org
BUG=399178

Review URL: https://codereview.chromium.org/603673002

git-svn-id: svn://svn.chromium.org/blink/trunk@182627 bbb929c8-8fbe-4397-9dbb-9b2b20218538