Make ReturnValue a friend of Persistent, so it can use operator*.

BUG=
R=dcarney@chromium.org, svenpanne@chromium.org

Review URL: https://codereview.chromium.org/15848010

Patch from Marja Hölttä <marja@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14999 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Recording array buffer views.

R=hpayer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/15562008

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15000 ce2b1a6d-e550-0410-aec6-3dcde31c8c00