constructors that only contain simple this assignments.

Make sure that constructors with declarations are not treated as
constructors with only simple this property assignments.

Review URL: http://codereview.chromium.org/601081

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3875 ce2b1a6d-e550-0410-aec6-3dcde31c8c00