Sped up hashCode by removing megamorphic call to _identityHashCode.

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 {
 
   // The VM has its own implementation of equals.
   bool operator ==(other) native "Object_equals";
 
   // Helpers used to implement hashCode. If a hashCode is used, we remember it
@@ skipping 40 matching lines @@
                          _symbolMapToStringMap(invocation.namedArguments));
   }
 
   /* patch */ Type get runtimeType native "Object_runtimeType";
 
   // Call this function instead of inlining instanceof, thus collecting
   // type feedback and reducing code size of unoptimized code.
   bool _instanceOf(instantiator_type_arguments, type, bool negate)
       native "Object_instanceOf";
 
+  // Group of functions for implementing fast simple instance of.
+  bool _simpleInstanceOf(type) native "Object_simpleInstanceOf";
+  bool _simpleInstanceOfTrue(type) => true;
+  bool _simpleInstanceOfFalse(type) => false;
+  
   bool _instanceOfDouble(bool negate) native "Object_instanceOfDouble";
   bool _instanceOfNum(bool negate) native "Object_instanceOfNum";
   bool _instanceOfInt(bool negate) native "Object_instanceOfInt";
   bool _instanceOfSmi(bool negate) native "Object_instanceOfSmi";
   bool _instanceOfString(bool negate) native "Object_instanceOfString";
 
   // Call this function instead of inlining 'as', thus collecting type
   // feedback. Returns receiver.
   _as(instantiator_type_arguments, type) native "Object_as";
 
   static _symbolMapToStringMap(Map<Symbol, dynamic> map) {
     var result = new Map<String, dynamic>();
     map.forEach((Symbol key, value) {
       result[internal.Symbol.getName(key)] = value;
     });
     return result;
   }
 }