Fix heap snapshot creation for Harmony collections.

R=yangguo@chromium.org
BUG=v8:2535
TEST=cctest/test-api/Regress2535

Review URL: https://codereview.chromium.org/12615005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@13897 ce2b1a6d-e550-0410-aec6-3dcde31c8c00