Enable calling the SetReference* & SetObjectGroupId functions with a Persistent<SubclassOfValue>.

This is needed for https://codereview.chromium.org/26792002/

BUG=
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/27512003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17253 ce2b1a6d-e550-0410-aec6-3dcde31c8c00