There was a bug in Object.defineProperty when used to add an indexed
property to an arguments object.  When converting the elements backing
store to dictionary mode, the parameter map in front of the backing
store does not change.

R=ager@chromium.org,karlklose@chromium.org

Review URL: http://codereview.chromium.org/7289011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8481 ce2b1a6d-e550-0410-aec6-3dcde31c8c00