Remove unused parameter.

This also fixes an analyzer warning since the param had the wrong type.

R=nweiz@google.com

Review URL: https://codereview.chromium.org//602983002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@40653 260f80e4-7a28-3924-810f-c04153c831b5