Use entities in CommonElements interface.

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

 // Copyright (c) 2011, 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 js_backend.namer;
 
 import 'dart:collection' show HashMap;
 
 import 'package:js_runtime/shared/embedded_names.dart' show JsGetName;
 
@@ skipping 618 matching lines @@
         return asName(functionTypeReturnTypeTag);
       case JsGetName.FUNCTION_TYPE_REQUIRED_PARAMETERS_TAG:
         return asName(functionTypeRequiredParametersTag);
       case JsGetName.FUNCTION_TYPE_OPTIONAL_PARAMETERS_TAG:
         return asName(functionTypeOptionalParametersTag);
       case JsGetName.FUNCTION_TYPE_NAMED_PARAMETERS_TAG:
         return asName(functionTypeNamedParametersTag);
       case JsGetName.IS_INDEXABLE_FIELD_NAME:
         return operatorIs(helpers.jsIndexingBehaviorInterface);
       case JsGetName.NULL_CLASS_TYPE_NAME:
-        return runtimeTypeName(commonElements.nullClass);
+        ClassElement nullClass = commonElements.nullClass;
+        return runtimeTypeName(nullClass);
       case JsGetName.OBJECT_CLASS_TYPE_NAME:
-        return runtimeTypeName(commonElements.objectClass);
+        ClassElement objectClass = commonElements.objectClass;
+        return runtimeTypeName(objectClass);
       case JsGetName.FUNCTION_CLASS_TYPE_NAME:
-        return runtimeTypeName(commonElements.functionClass);
+        ClassElement functionClass = commonElements.functionClass;
+        return runtimeTypeName(functionClass);
       default:
         reporter.reportErrorMessage(node, MessageKind.GENERIC,
             {'text': 'Error: Namer has no name for "$name".'});
         return asName('BROKEN');
     }
   }
 
   /// Return a reference to the given [name].
   ///
   /// This is used to ensure that every use site of a name has a unique node so
@@ skipping 1548 matching lines @@
   void addSuggestion(String original, String suggestion) {
     assert(!_suggestedNames.containsKey(original));
     _suggestedNames[original] = suggestion;
   }
 
   bool hasSuggestion(String original) => _suggestedNames.containsKey(original);
   bool isSuggestion(String candidate) {
     return _suggestedNames.containsValue(candidate);
   }
 }