Use Object::null_instance and Object::null_function and do not create Handles everytime.

runtime/vm/class_finalizer.cc

 // Copyright (c) 2013, 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/class_finalizer.h"
 
 #include "vm/code_generator.h"
 #include "vm/flags.h"
 #include "vm/heap.h"
 #include "vm/isolate.h"
@@ skipping 1398 matching lines @@
                             /* is_static = */ true,
                             /* is_const = */ field.is_const(),
                             /* is_abstract = */ false,
                             /* is_external = */ false,
                             /* is_native = */ false,
                             cls,
                             field.token_pos()));
           getter.set_result_type(type);
           getter.set_is_debuggable(false);
           cls.AddFunction(getter);
-          field.set_value(Instance::Handle(I, Object::sentinel().raw()));
+          field.set_value(Object::sentinel());
         }
       }
     }
   }
   // Collect interfaces, super interfaces, and super classes of this class.
   const GrowableObjectArray& interfaces =
       GrowableObjectArray::Handle(I, GrowableObjectArray::New());
   CollectInterfaces(cls, interfaces);
   // Include superclasses in list of interfaces and super interfaces.
   super_class = cls.SuperClass();
@@ skipping 1789 matching lines @@
   ASSERT(fields_array.Length() == ByteBuffer::NumberOfFields());
   field ^= fields_array.At(0);
   ASSERT(field.Offset() == ByteBuffer::data_offset());
   name ^= field.name();
   expected_name ^= String::New("_data");
   ASSERT(String::EqualsIgnoringPrivateKey(name, expected_name));
 #endif
 }
 
 }  // namespace dart