Add ClosureClassMaps super interface for ClosureTask

pkg/compiler/lib/src/js_backend/interceptor_data.dart

Index: pkg/compiler/lib/src/js_backend/interceptor_data.dart
diff --git a/pkg/compiler/lib/src/js_backend/interceptor_data.dart b/pkg/compiler/lib/src/js_backend/interceptor_data.dart
index f22802f750c9796ac74acf3004de470974dc8cde..f6d8eff280550147f5fb10d54a16c153be437438 100644
--- a/pkg/compiler/lib/src/js_backend/interceptor_data.dart
+++ b/pkg/compiler/lib/src/js_backend/interceptor_data.dart
@@ -6,7 +6,7 @@ library js_backend.interceptor_data;
 
 import '../common/names.dart' show Identifiers;
 import '../common_elements.dart' show CommonElements, ElementEnvironment;
-import '../elements/elements.dart' show MemberElement;
+import '../elements/elements.dart' show ConstructorBodyElement;
 import '../elements/entities.dart';
 import '../elements/types.dart';
 import '../js/js.dart' as jsAst;
@@ -89,9 +89,10 @@ class InterceptorDataImpl implements InterceptorData {
       this._interceptedClasses,
       this._classesMixedIntoInterceptedClasses);
 
-  bool isInterceptedMethod(MemberElement element) {
+  bool isInterceptedMethod(MemberEntity element) {
     if (!element.isInstanceMember) return false;
-    if (element.isGenerativeConstructorBody) {
+    // TODO(johnniwinther): Avoid this hack.
+    if (element is ConstructorBodyElement) {
       return _nativeData.isNativeOrExtendsNative(element.enclosingClass);
     }
     return _interceptedElements[element.name] != null;