Ensure constructorName symbols include private manglings.

tests/lib/mirrors/constructor_private_name_test.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.
+
+library test.constructors_test;
+
+// Regression test for C1 bug.
+
+import 'dart:mirrors';
+
+import 'package:expect/expect.dart';
+
+class Foo {
+  Foo._private();
+}
+
+class _Foo {
+  _Foo._private();
+}
+
+main() {
+  ClassMirror fooMirror = reflectClass(Foo);
+  Symbol constructorName =
+      (fooMirror.declarations[#Foo._private] as MethodMirror).constructorName;
+  fooMirror.newInstance(constructorName, []);
+
+  ClassMirror _fooMirror = reflectClass(_Foo);
+  constructorName =
+      (_fooMirror.declarations[#_Foo._private] as MethodMirror).constructorName;
+  _fooMirror.newInstance(constructorName, []);
+}