Use entities in CommonElements interface.

pkg/compiler/lib/src/js_emitter/startup_emitter/emitter.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.js_emitter.startup_emitter;
 
 import 'package:js_runtime/shared/embedded_names.dart'
     show JsBuiltin, METADATA, STATIC_FUNCTION_NAME_TO_CLOSURE, TYPES;
 
 import '../../common.dart';
@@ skipping 128 matching lines @@
   js.Expression typeAccess(Element element) {
     return _globalPropertyAccess(element);
   }
 
   @override
   js.Template templateForBuiltin(JsBuiltin builtin) {
     String typeNameProperty = ModelEmitter.typeNameProperty;
 
     switch (builtin) {
       case JsBuiltin.dartObjectConstructor:
-        return js.js.expressionTemplateYielding(
-            typeAccess(_compiler.commonElements.objectClass));
+        ClassElement objectClass = _compiler.commonElements.objectClass;
+        return js.js.expressionTemplateYielding(typeAccess(objectClass));
 
       case JsBuiltin.isCheckPropertyToJsConstructorName:
         int isPrefixLength = namer.operatorIsPrefix.length;
         return js.js.expressionTemplateFor('#.substring($isPrefixLength)');
 
       case JsBuiltin.isFunctionType:
         return _backend.rtiEncoder.templateForIsFunctionType;
 
       case JsBuiltin.rawRtiToJsConstructorName:
         return js.js.expressionTemplateFor("#.$typeNameProperty");
@@ skipping 37 matching lines @@
   @override
   int generatedSize(OutputUnit unit) {
     Fragment key = _emitter.outputBuffers.keys
         .firstWhere((Fragment fragment) => fragment.outputUnit == unit);
     return _emitter.outputBuffers[key].length;
   }
 
   @override
   void invalidateCaches() {}
 }