Promoting elements transitions to their own field.

Promoting elements transitions to their own field.
This is a first step towards separating all transitions from the property descriptions. If we link the property descriptions from the transition object, this will in allow the descriptor array (property descriptions) to become immutable.

Review URL: https://chromiumcodereview.appspot.com/10444055

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11750 ce2b1a6d-e550-0410-aec6-3dcde31c8c00