while performing GlobalHandles::PostGarbageCollectionProcessing as those might be already deleted (in C++ sense).

Review URL: http://codereview.chromium.org/173060

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2724 ce2b1a6d-e550-0410-aec6-3dcde31c8c00