Remove remaining HandleScope::Close usage

For some reason, this is only caught when compiling with chromium on
Mac.

BUG=none
R=verwaest@chromium.org, dslomov@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/99263002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18209 ce2b1a6d-e550-0410-aec6-3dcde31c8c00