Avoid use of empty string as a property name.

sdk/lib/_internal/compiler/implementation/js_backend/namer.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/namer.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart b/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart
index 33804f656a471038d9ed31dcfb605763e2bb34ab..8ac77b0f51351049b8cf95904938d7f66aa06acc 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart
@@ -227,6 +227,8 @@ class Namer implements ClosureNamer {
   final String methodsWithOptionalArgumentsField =
       r'$methodsWithOptionalArguments';
 
+  final String classDescriptorProperty = r'^';
+
   // Name of property in a class description for the native dispatch metadata.
   final String nativeSpecProperty = '%';
 
@@ -290,6 +292,7 @@ class Namer implements ClosureNamer {
       case 'SETTER_PREFIX': return setterPrefix;
       case 'CALL_CATCH_ALL': return callCatchAllName;
       case 'REFLECTABLE': return reflectableField;
+      case 'CLASS_DESCRIPTOR_PROPERTY': return classDescriptorProperty;
       default:
         compiler.reportError(
             node, MessageKind.GENERIC,