1. Build error:
  2. Transforms {Dart2JS on HelloDart|web/hellodart.dart} all emitted asset HelloDart|web/hellodart.dart.js.
  3. [Dart2JS on HelloDart|web/hellodart.html_bootstrap.dart]:
  4. packages/observe/src/path_observer.dart:10:1: Info: Import of 'dart:mirrors'.
  5. import 'dart:mirrors';