Implement Smi.toString in Dart instead of calling to C++ natives. Large performance improvement.

R=asiva@google.com

Review URL: https://codereview.chromium.org//14629015

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@22341 260f80e4-7a28-3924-810f-c04153c831b5
1 file changed