Make IDL Callbacks non-refcounted by default

Source/bindings/v8/V8Callback.h

 /*
 * Copyright (C) 2012 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
@@ skipping 34 matching lines @@
 
 enum CallbackAllowedValueFlag {
     CallbackAllowUndefined = 1,
     CallbackAllowNull = 1 << 1
 };
 
 typedef unsigned CallbackAllowedValueFlags;
 
 // 'FunctionOnly' is assumed for the created callback.
 template <typename V8CallbackType>
-PassRefPtr<V8CallbackType> createFunctionOnlyCallback(v8::Local<v8::Value> value, bool& succeeded, v8::Isolate* isolate, CallbackAllowedValueFlags acceptedValues = 0)
+PassOwnPtr<V8CallbackType> createFunctionOnlyCallback(v8::Local<v8::Value> value, bool& succeeded, v8::Isolate* isolate, CallbackAllowedValueFlags acceptedValues = 0)
 {
     succeeded = true;
 
     if (value->IsUndefined() && (acceptedValues & CallbackAllowUndefined))
-        return 0;
+        return nullptr;
 
     if (value->IsNull() && (acceptedValues & CallbackAllowNull))
-        return 0;
+        return nullptr;
 
     if (!value->IsFunction()) {
         succeeded = false;
         setDOMException(TypeMismatchError, isolate);
-        return 0;
+        return nullptr;
     }
 
     return V8CallbackType::create(value, getExecutionContext());
 }
 
 } // namespace WebCore
 
 #endif // V8Callback_h