Revert 'Introduce phantom weak handles in the API and use them internally for debug info'

Revert of https://codereview.chromium.org/649563006/ due to layout test
failures.
BUG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/677403002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24901 ce2b1a6d-e550-0410-aec6-3dcde31c8c00