Add Timeout to this test to get the mac and win incremental bots green for now

TBR=vsm@google.com

BUG=

Review URL: https://codereview.chromium.org//666383003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@41300 260f80e4-7a28-3924-810f-c04153c831b5