Prevent false positive from GCMole in DeferredFormatStackTrace.

R=yangguo@chromium.org
TEST=gcmole

Review URL: https://codereview.chromium.org/14416010

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14447 ce2b1a6d-e550-0410-aec6-3dcde31c8c00