Avoid use of empty string as a property name.

sdk/lib/_internal/compiler/implementation/js_emitter/class_builder.dart

 // Copyright (c) 2013, 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.
 
 part of dart2js.js_emitter;
 
 /**
  * A data structure for collecting fragments of a class definition.
  */
 class ClassBuilder {
   final List<jsAst.Property> properties = <jsAst.Property>[];
   final List<String> fields = <String>[];
 
   String superName;
   String nativeName;
   String functionType;
   List<jsAst.Node> fieldMetadata;
 
+  final Namer namer;
+
   /// Set to true by user if class is indistinguishable from its superclass.
   bool isTrivial = false;
 
+  ClassBuilder(this.namer);
+
   // Has the same signature as [DefineStubFunction].
   void addProperty(String name, jsAst.Expression value) {
     properties.add(new jsAst.Property(js.string(name), value));
   }
 
   void addField(String field) {
     fields.add(field);
   }
 
   jsAst.ObjectInitializer toObjectInitializer() {
@@ skipping 11 matching lines @@
     buffer.writeAll(fields, ',');
     var classData = js.string('$buffer');
     if (fieldMetadata != null) {
       // If we need to store fieldMetadata, classData is turned into an array,
       // and the field metadata is appended. So if classData is just a string,
       // there is no field metadata.
       classData =
           new jsAst.ArrayInitializer.from([classData]..addAll(fieldMetadata));
     }
     var fieldsAndProperties =
-        [new jsAst.Property(js.string(''), classData)]
+        [new jsAst.Property(js.string(namer.classDescriptorProperty),
+                            classData)]
         ..addAll(properties);
     return new jsAst.ObjectInitializer(fieldsAndProperties, isOneLiner: false);
   }
 
 }