Revert of Service Worker: Make ServiceWorkerRegistration.update() return a promise. (Blink 1/3)

Revert of Service Worker: Make ServiceWorkerRegistration.update() return a promise. (Blink 1/3) (patchset #2 id:20001 of https://codereview.chromium.org/1267703003/)

Reason for revert:
Sorry, this seems to cause http/tests/serviceworker/update.html to fail consistently on WebKit Linux Leak and WebKit Linux Oilpan Leak with the following error:

(leak detected: ({"numberOfLiveActiveDOMObjects":[2,3]}))

See flakiness dashboard:

http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=http%2Ftests%2Fserviceworker%2Fupdate.html&testType=layout-tests

And example failed build:

http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Leak/builds/12981

Original issue's description:
> Service Worker: Make ServiceWorkerRegistration.update() return a promise. (Blink 1/3)
> 
> As per the resolution of f2f, ServiceWorkerRegistration.update() should return a
> promise that transforms the promise returned by Update algorithm.
> 
> In this CL, ServiceWorkerContextCore::UpdateServiceWorker method has been
> overloaded to cover two invocation paths: a scheduled update without a
> provider_host and a callback (Soft Update in the spec) and a call initiated from
> the script surface using ServiceWorkerRegistration.update().
> 
> This is a web-exposed API change. But it has no compatibility risk because 
> existing user code doesn't expect to receive anything from update().
> 
> Spec: https://slightlyoff.github.io/ServiceWorker/spec/service_worker/#service-worker-registration-update
> Spec discussion: https://github.com/slightlyoff/ServiceWorker/issues/311
> 
> Companion CL (Chromium): https://codereview.chromium.org/1270513002/
> Companion CL (Blink layout test): https://codereview.chromium.org/1268663003/
> 
> BUG=513655
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=199814

TBR=l.gombos@samsung.com,jinho.bang@samsung.com,falken@chromium.org,kinuko@chromium.org,nhiroki@chromium.org,michaeln@chromium.org,tkent@chromium.org,jungkee.song@samsung.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=513655
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=199830

[johnme, 2015-07-31 13:25:55]

Created Revert of Service Worker: Make ServiceWorkerRegistration.update() return
a promise. (Blink 1/3)

[commit-bot: I haz the power, 2015-07-31 13:26:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1264143002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1264143002/1

[commit-bot: I haz the power, 2015-07-31 13:26:50]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=199830

[tkent, 2015-08-02 23:17:52]

lgtm