These constants only work for dart2js because neither Dartium nor the isolate
API support defining them.

BUG= http://dartbug.com/15806
R=rnystrom@google.com

Review URL: https://codereview.chromium.org//1106713003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge@45416 260f80e4-7a28-3924-810f-c04153c831b5