chore: add dartdoc compliance checks to build

Closes #3582

modules/angular2/core.ts

@@ -23,7 +23,6 @@ export {LifeCycle} from 'angular2/src/core/life_cycle/life_cycle';
 
 export {ElementRef} from 'angular2/src/core/compiler/element_ref';
 export {TemplateRef} from 'angular2/src/core/compiler/template_ref';
-export {RenderElementRef} from 'angular2/src/render/api';
 export {ViewRef, HostViewRef, ProtoViewRef} from 'angular2/src/core/compiler/view_ref';
 export {ViewContainerRef} from 'angular2/src/core/compiler/view_container_ref';
 export {ComponentRef} from 'angular2/src/core/compiler/dynamic_component_loader';

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);
 }