Revert of Stop ServiceWorker context when no controllee is associated (and when all refs are dropped)

Revert of Stop ServiceWorker context when no controllee is associated (and when all refs are dropped) (https://codereview.chromium.org/272183005/)

Reason for revert:
Has memory leaks in
EmbeddedWorkerInstanceTest.InstanceDestroyedBeforeStartFinishes

Original issue's description:
> Stop ServiceWorker context when no controllee is associated (and when all refs are dropped)
> 
> Currently we stop the ServiceWorker thread/context when:
> 1. After all documents that are controlled by the SW are closed, with a delay (5 min)
> 2. All references to the version are dropped (i.e. in dtor)
> 
> In the current impl/codebase a worker is immediately stopped by 2
> in most cases.
> 
> The same stop timer (ScheduleStopWorker()) could be probably called
> each time handling event is finished to stop the worker more 
> aggressively, though this patch doesn't do so.
> 
> BUG=372673
> TEST=tested manually with chrome://serviceworker-internals/
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=270971

TBR=michaeln@chromium.org,horo@chromium.org,kinuko@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=372673
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=270976

[Adrian Kuegel, 2014-05-16 09:52:37]

Created Revert of Stop ServiceWorker context when no controllee is associated
(and when all refs are dropped)