- Add definition of "int hashCode()" to Object.

runtime/lib/object_patch.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.
 
 patch class Object {
+
+  // Helpers used to implement hashCode. If a hashCode is used we remember it
+  // using an Expando object. A new hashCode value is calculated using a Random
+  // number generator.
+  static Expando _hashCodeExp = new Expando("Object.hashCode");
+  static Random _hashCodeRnd = new Random();
+
+  /* patch */ int hashCode() {
+    var result = _hashCodeExp[this];
+    if (result == null) {
+      result = _hashCodeRnd.nextInt(0x40000000);  // Stay in Smi range.
+      _hashCodeExp[this] = result;
+    }
+    return result;
+  }
+
   /* patch */ String toString() => _toString(this);
 
   /* patch */ void noSuchMethod(String functionName, List args) {
     _noSuchMethod(this, functionName, args);
   }
 
   static void _noSuchMethod(Object obj, String functionName, List args)
       native "Object_noSuchMethod";
 
   static String _toString(Object obj) native "Object_toString";
 }