Incorrectly flags concrete type arguments as non-const.

[peter-ahe-google]

class Foo {
  final Bar<Foo> bar = const Bar<Foo>();
}

class Bar<T extends Foo> {
  const Bar();
}

main() {
  print(new Foo());
}

generic.dart:2:24: error: non constant field must be initialized in constructor
  final Bar<Foo> bar = const Bar<Foo>();
                       ^^^^^^^^^^^^^^^^
compilation failed with 1 errors

[anders-sandholm]

Removed Area-Frog label.
Added Area-Dart2JS, FromAreaFrog labels.

[kasperl]

Added WontFix label.