partial review for const and final

I've been unable to run tests, so I'd love someone to take a look there.
Try throwing this into http://try.dartlang.org/

```dart
// Prints a greeting.
void main() {
  _foo();
}

void _foo({bool isTrue: true, bool isFalse: false}) {
  print([isTrue, isFalse]);
}
```