Make TransitionArray internal references originate from TA in heap snapshot.

TransitionArray references were added to the TA's map object instead
of TA itself.

R=verwaest@chromium.org, yurys@chromium.org

Review URL: https://codereview.chromium.org/19265002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15692 ce2b1a6d-e550-0410-aec6-3dcde31c8c00