refactor(dart): Format Dart code

Use the dart formatter to clean up all pure Dart code.

Closes #4832

modules/angular2/test/core/reflection/reflector_common.dart

@@ -31,4 +31,4 @@ PropDecorator propDecorator(value) {
 class HasGetterAndSetterDecorators {
   @PropDecorator("get") get a {}
   @PropDecorator("set") set a(v) {}
-}
+}