Remove ParameterAdapters for bindings classes.

lib/dom/templates/dom/native/cpp_callback_header.template

 // 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.
 
 // WARNING: Do not edit - generated code.
 
 #ifndef Dart$(INTERFACE)_h
 #define Dart$(INTERFACE)_h
 
 #include "ActiveDOMCallback.h"
 #include "DartCallback.h"
 #include "DartDOMWrapper.h"
 #include "$(INTERFACE).h"
 
 namespace WebCore {
 
 class Dart$(INTERFACE) : public $(INTERFACE), public ActiveDOMCallback {
 public:
     typedef $(INTERFACE) NativeType;
 
-    static PassRefPtr<NativeType> toNative(Dart_Handle object, Dart_Handle& exception)
+    static PassRefPtr<NativeType> create(Dart_Handle object, DartUtilities::ConversionFlag flag, Dart_Handle& exception)
     {
+        if (flag == DartUtilities::ConvertNullToDefaultValue && Dart_IsNull(object))
+            return 0;
         return adoptRef(new Dart$(INTERFACE)(object, exception, DartUtilities::scriptExecutionContext()));
     }
 $HANDLERS
 
 private:
     Dart$(INTERFACE)(Dart_Handle object, Dart_Handle& exception, ScriptExecutionContext* context)
         : ActiveDOMCallback(context)
         , m_callback(object, exception)
     {
     }
 
     DartCallback m_callback;
 };
 
 }
 
 #endif // Dart$(INTERFACE)_h