Add Object.hashCodeOf to get the default hashCode of an object.

sdk/lib/core/object.dart

 // Copyright (c) 2012, 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 dart.core;
 
 /**
  * The base class for all Dart objects.
  *
  * Because Object is the root of the Dart class hierarchy,
@@ skipping 75 matching lines @@
    *
    * The default behavior of [noSuchMethod] is to throw a
    * [noSuchMethodError].
    */
   external dynamic noSuchMethod(Invocation invocation);
 
   /**
    * A representation of the runtime type of the object.
    */
   external Type get runtimeType;
+
+  /**
+   * Returns the same value as [hashCode] on [object] would.

[Ivan Posva, 2013/09/24 06:22:11]

This is not true, as is stated right on the next line.

+   *
+   * If [object] hasn't overridden [hashCode] from [Object], this is the
+   * same as `object.hashCode`. This method can be used to get the object's
+   * hashCode event if `hashCode` has been overridden.

[Ivan Posva, 2013/09/24 06:22:11]

What this should state is that this returns the hash code which goes together
with the identical function, in a similar manner to hashCode and operator ==.

+   */
+  external static int hashCodeOf(Object object);
 }