Revert of [Extension ServiceWorkers] Blink: Passing v8::context to extensions dispatcher

Revert of [Extension ServiceWorkers] Blink: Passing v8::context to extensions dispatcher (patchset #5 id:190001 of https://codereview.chromium.org/1264913002/ )

Reason for revert:
Sorry to revert this change. It's suspected of breaking webkit_unit_tests test CompositorWorkerManagerTest.CreatingSecondDuringTerminationOfFirst:
http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Mac10.8/builds/39874

Original issue's description:
> [Extension ServiceWorkers] Blink: Passing v8::context to extensions dispatcher
> 
> Pass the v8::context from the worker thread up to the extensions dispatcher.  
> 
> In order to expose any kind of custom binding (i.e., javascript callback into C++ code) for the service worker context, we need to be alerted of when the context is created, so that we can inject them.  For most contexts, this is done through the blink notification (didCreateScriptContext), but that doesn't cover
> worker contexts.
> 
> Please view https://codereview.chromium.org/1256323008/ for the continuation of this implementation in chrome.
> 
> BUG=501569
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200277

TBR=dcheng@chromium.org,rdevlin.cronin@chromium.org,sadrul@chromium.org,annekao@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=501569
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200376

[falken, 2015-08-12 03:17:19]

Created Revert of [Extension ServiceWorkers] Blink: Passing v8::context to
extensions dispatcher

[commit-bot: I haz the power, 2015-08-12 03:17:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1287903002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1287903002/1

[commit-bot: I haz the power, 2015-08-12 03:18:07]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=200376