Move serviceworker/ module to oilpan

- This CL doesn't move InstallEvent and InstallPhaseEvent since we need to move Event first.

- This CL doesn't move ServiceWorkerGlobalScope since we need to move WorkerGlobalScope first.

- This CL doesn't move ServiceWorkerThread since we need to move WorkerThread first.

BUG=340522
TBR=abarth (for web/)

Review URL: https://codereview.chromium.org/153083006

git-svn-id: svn://svn.chromium.org/blink/trunk@166694 bbb929c8-8fbe-4397-9dbb-9b2b20218538