Revert "First attempt at providing default traits for PersistentValueMap."

This reverts r20038.

TBR=vogelheim@chromium.org

Review URL: https://codereview.chromium.org/203553002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20042 ce2b1a6d-e550-0410-aec6-3dcde31c8c00