1. Remove unnecessary superlcass LConstant.
2. Use hydrogen accessor instead of duplicating the value.

Review URL: http://codereview.chromium.org/6410120

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6672 ce2b1a6d-e550-0410-aec6-3dcde31c8c00