Clusterfuzz identified overflow check needed in dehoisting.

BUG=380092
R=danno@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/315593002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21708 ce2b1a6d-e550-0410-aec6-3dcde31c8c00