This makes sure that the first hit is used when dumping heap constants
and hence "TheHoleValue" is not overwritten with other roots that are
initialized to the hole as well.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/21639004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16058 ce2b1a6d-e550-0410-aec6-3dcde31c8c00