Revert 166694 "Move serviceworker/ module to oilpan"

We decided not to move ServiceWorker to oilpan at the moment,
since ServiceWorker is actively being developed and oilpan changes
will confuse the development. We will get back to ServiceWorker later.

> 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

TBR=haraken@chromium.org

Review URL: https://codereview.chromium.org/158583002

git-svn-id: svn://svn.chromium.org/blink/trunk@166773 bbb929c8-8fbe-4397-9dbb-9b2b20218538