Avoid use of empty string as a property name.

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

Index: sdk/lib/_internal/compiler/implementation/js_emitter/class_builder.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_emitter/class_builder.dart b/sdk/lib/_internal/compiler/implementation/js_emitter/class_builder.dart
index 53e32d8de8789e56ec417f7c048f3eb78ac0bd1e..044368bb9d53833e27d581ce19ca2ef4a4096585 100644
--- a/sdk/lib/_internal/compiler/implementation/js_emitter/class_builder.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_emitter/class_builder.dart
@@ -16,9 +16,13 @@ class ClassBuilder {
   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));
@@ -50,7 +54,8 @@ class ClassBuilder {
           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);
   }