Revert of [Oilpan] Fix wrong usage of HeapCountedSet<EventTarget*> (patchset #3 id:80001 of https://codereview.chromium.org/1401033002/ )

Reason for revert:
Broke a number of tests on all Oilpan bots,

 http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20Oilpan/builds/29326

Lazy sweeping of EventTargetSet related.

Original issue's description:
> Fix wrong usage of HeapCountedSet<EventTarget*>
>
> BUG=515524
>
> Committed: https://crrev.com/0ab9a39b2347bc686cb6c2a7464acfebe3d4bd10
> Cr-Commit-Position: refs/heads/master@{#353714}

TBR=oilpan-reviews@chromium.org,haraken@chromium.org,peria@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=515524

Review URL: https://codereview.chromium.org/1405513003

Cr-Commit-Position: refs/heads/master@{#353756}
1 file changed