Address hint discovered by dart2js: add hashCode to source_maps.Span

R=dgrove@google.com

Review URL: https://codereview.chromium.org//19315003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/source_maps@25050 260f80e4-7a28-3924-810f-c04153c831b5
1 file changed
tree: f45749be9a939aec0b1f181ec28167381955739e
  1. pkgs/