Cleanup the core/object.dart file.

lib/core/identical.dart

Index: lib/core/identical.dart
diff --git a/lib/html/doc/nodoc-src/_AudioElementFactoryProvider.dart b/lib/core/identical.dart
similarity index 66%
copy from lib/html/doc/nodoc-src/_AudioElementFactoryProvider.dart
copy to lib/core/identical.dart
index 0c2c0f3949ca2a6f6b526367914873a8d94f0598..5de366f26324549af1b0cfb3aefeabe0b3f32e72 100644
--- a/lib/html/doc/nodoc-src/_AudioElementFactoryProvider.dart
+++ b/lib/core/identical.dart
@@ -2,6 +2,7 @@
 // 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.
 
-class _AudioElementFactoryProvider {
-  factory AudioElement([String src = null]) => null;
-}
+/**
+ * Check whether two references are to the same object.
+ */
+bool identical(Object a, Object b) => a === b;