Make the implementations of InstanceMirror.hashCode use dart:core's identityHashCode.

runtime/lib/mirrors_impl.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.
 
 // VM-specific implementation of the dart:mirrors library.
 
 import "dart:collection";
 
 // These values are allowed to be passed directly over the wire.
 bool _isSimpleValue(var value) {
@@ skipping 284 matching lines @@
   }
 
   String toString() => 'InstanceMirror on ${Error.safeToString(_reflectee)}';
 
   bool operator ==(other) {
     return other is _LocalInstanceMirrorImpl &&
            identical(_reflectee, other._reflectee);
   }
 
   int get hashCode {
-    // If the reflectee is a double or bignum, use the base hashCode to preserve
-    // the illusion that boxed numbers with the same value are identical. If the
-    // reflectee is a Smi, use the base hashCode because Object.hashCode does
-    // not work for non-heap objects. Otherwise, use Object.hashCode to maintain
-    // correctness even if a user-defined hashCode returns different values for
-    // successive invocations.
-    var h = _reflectee is num ? _reflectee.hashCode : _identityHash(_reflectee);
     // Avoid hash collisions with the reflectee. This constant is in Smi range
     // and happens to be the inner padding from RFC 2104.
-    return h ^ 0x36363636;
+    return identityHashCode(_reflectee) ^ 0x36363636;
   }
 
-  static _identityHash(reflectee)
-      native "InstanceMirror_identityHash";
-
   // Override to include the receiver in the arguments.
   InstanceMirror invoke(Symbol memberName,
                         List positionalArguments,
                         [Map<Symbol, dynamic> namedArguments]) {
     int numPositionalArguments = positionalArguments.length + 1;  // Receiver.
     int numNamedArguments = namedArguments != null ? namedArguments.length : 0;
     int numArguments = numPositionalArguments + numNamedArguments;
     List arguments = new List(numArguments);
     arguments[0] = _reflectee;  // Receiver.
     arguments.setRange(1, numPositionalArguments, positionalArguments);
@@ skipping 1001 matching lines @@
     if (typeMirror == null) {
       typeMirror = makeLocalTypeMirror(key);
       _instanitationCache[key] = typeMirror;
       if (typeMirror is ClassMirror && !typeMirror._isGeneric) {
         _declarationCache[key] = typeMirror;
       }
     }
     return typeMirror;
   }
 }