Add method to html_dartium utils to check for NSM errors

BUG=
R=vsm@google.com

Review URL: https://codereview.chromium.org//21676003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@25741 260f80e4-7a28-3924-810f-c04153c831b5
2 files changed