Revert of Forbid creating new wrapper from SetWrapperReferenceTo

Revert of Forbid creating new wrapper from SetWrapperReferenceTo (https://codereview.chromium.org/332643003/)

Reason for revert:
There seems to be an existing bug which hits this callpath. Reverting the change until the bug is fixed.

Original issue's description:
> Forbid creating new wrapper from SetWrapperReferenceTo
> 
> SetWrapperReferenceTo IDL attribute is a hack to use V8 wrapper reference
> to avoid reference cycles in Blink. The |visitDOMWrapper| callback is
> used to create a temporary strong reference between the wrappers in GC
> prologue.
> 
> Before this patch, |visitDOMWrapper| was allowed to create a new wrapper
> if the wrapper for target object didn't exist. However this is dangerous,
> as the target object may be already destructed. The target wrapper must
> already exist for this reference hack to work correctly.
> 
> This patch forbids creating a new wrapper from |visitDOMWrapper| callback,
> and adds an ASSERT that checks that the target object wrapper already
> exists.
> 
> BUG=None
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=175998

TBR=nbarth@chromium.org,haraken@chromium.org
BUG=384459
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=176281

[kouhei (in TOK), 2014-06-17 03:48:43]

Created Revert of Forbid creating new wrapper from SetWrapperReferenceTo

[haraken, 2014-06-17 03:49:30]

LGTM. Let's revert it at the moment and fix the underlying bug!

[commit-bot: I haz the power, 2014-06-17 03:50:13]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/kouhei@chromium.org/332183008/1

[commit-bot: I haz the power, 2014-06-17 04:56:58]

Change committed as 176281