Crashes unregistering DOMWindowProperties while releasing CachedPages

Reviewed by Jessie Berlin.

This patch rewrites DOMWindowProperty to always keep direct track of the DOMWindow
it has registered with and to only ever unregister from that very same DOMWindow.

No new tests. (While the direct cause of the crash is understood, reproducing it is not)

* page/DOMWindowProperty.cpp:
(WebCore::DOMWindowProperty::DOMWindowProperty):
(WebCore::DOMWindowProperty::~DOMWindowProperty):
(WebCore::DOMWindowProperty::disconnectFrameForPageCache):
(WebCore::DOMWindowProperty::reconnectFrameFromPageCache):
(WebCore::DOMWindowProperty::willDestroyGlobalObjectInCachedFrame):
(WebCore::DOMWindowProperty::willDestroyGlobalObjectInFrame):
(WebCore::DOMWindowProperty::willDetachGlobalObjectFromFrame):
* page/DOMWindowProperty.h:
(DOMWindowProperty):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@119136 268f45cc-cd09-0410-ab3c-d52691b4dbfc