Avoid creation of a handle when ssetting native fields for the first time.

runtime/vm/object.cc

 // 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.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 11933 matching lines @@
   }
   return false;
 }
 
 
 void Instance::SetNativeField(int index, intptr_t value) const {
   ASSERT(IsValidNativeIndex(index));
   Object& native_fields = Object::Handle(*NativeFieldsAddr());
   if (native_fields.IsNull()) {
     // Allocate backing storage for the native fields.
-    const Class& cls = Class::Handle(clazz());
-    int num_native_fields = cls.num_native_fields();
-    native_fields = TypedData::New(kIntPtrCid, num_native_fields);
+    native_fields = TypedData::New(kIntPtrCid, NumNativeFields());
     StorePointer(NativeFieldsAddr(), native_fields.raw());
   }
   intptr_t byte_offset = index * sizeof(intptr_t);
   TypedData::Cast(native_fields).SetIntPtr(byte_offset, value);
 }
 
 
 bool Instance::IsClosure() const {
   const Class& cls = Class::Handle(clazz());
   return cls.IsSignatureClass();
@@ skipping 5489 matching lines @@
   return "_MirrorReference";
 }
 
 
 void MirrorReference::PrintToJSONStream(JSONStream* stream, bool ref) const {
   Instance::PrintToJSONStream(stream, ref);
 }
 
 
 }  // namespace dart