chore: add dartdoc compliance checks to build

Closes #3582

modules/angular2/src/test_lib/spies.dart

@@ -4,27 +4,27 @@ import 'package:angular2/src/change_detection/change_detection.dart';
 import 'package:angular2/di.dart';
 import './test_lib.dart';
 
-@proxy()
+@proxy
 class SpyChangeDetector extends SpyObject implements ChangeDetector {
   noSuchMethod(m) => super.noSuchMethod(m);
 }
 
-@proxy()
+@proxy
 class SpyProtoChangeDetector extends SpyObject implements ProtoChangeDetector {
   noSuchMethod(m) => super.noSuchMethod(m);
 }
 
-@proxy()
+@proxy
 class SpyPipe extends SpyObject implements Pipe {
   noSuchMethod(m) => super.noSuchMethod(m);
 }
 
-@proxy()
+@proxy
 class SpyDependencyProvider extends SpyObject implements DependencyProvider {
   noSuchMethod(m) => super.noSuchMethod(m);
 }
 
-@proxy()
+@proxy
 class SpyChangeDetectorRef extends SpyObject implements ChangeDetectorRef {
   noSuchMethod(m) => super.noSuchMethod(m);
 }