Revert of Enable Service Workers, including the onfetch event, by default. (patchset #1 id:1 of https://codereview.chromium.org/680473002/)

Reason for revert:
Directory restriction of ServiceWorker sope patch (https://codereview.chromium.org/672383003/) is reverted.

We should not enable ServiceWorker without this restriction for security reason.

I will revert this patch after these patches will land.
[1/3 blink] https://codereview.chromium.org/674133004/
 Update LayoutTests to be subject to the directory restrictions.
[2/3 chromium] https://codereview.chromium.org/674133004/
 Introduce the directory restriction in Chromium side.
[3/3 blink] https://codereview.chromium.org/681483004/
 Introduce the directory restriction in Blink side and update LayoutTest.


Original issue's description:
> Enable Service Workers, including the onfetch event, by default.
> 
> BUG=364627
> TEST=virtual/stable/webexposed
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=184340

TBR=jochen@chromium.org,tkent@chromium.org,falken@chromium.org,dominicc@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=364627

Review URL: https://codereview.chromium.org/678843002

git-svn-id: svn://svn.chromium.org/blink/trunk@184400 bbb929c8-8fbe-4397-9dbb-9b2b20218538