Oilpan: Enable oilpan for callback classes

Source/core/clipboard/DataTransferItem.cpp

 /*
  * Copyright (C) 2011 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 51 matching lines @@
     return String();
 }
 
 String DataTransferItem::type() const
 {
     if (!m_dataTransfer->canReadTypes())
         return String();
     return m_item->type();
 }
 
-void DataTransferItem::getAsString(ExecutionContext* context, PassOwnPtrWillBeRawPtr<StringCallback> callback) const
+void DataTransferItem::getAsString(ExecutionContext* context, StringCallback* callback) const
 {
     if (!m_dataTransfer->canReadData())
         return;
     if (!callback || m_item->kind() != DataObjectItem::StringKind)
         return;
 
     StringCallback::scheduleCallback(callback, context, m_item->getAsString(), "DataTransferItem.getAsString");
 }
 
 PassRefPtrWillBeRawPtr<Blob> DataTransferItem::getAsFile() const
@@ skipping 11 matching lines @@
 }
 
 void DataTransferItem::trace(Visitor* visitor)
 {
     visitor->trace(m_dataTransfer);
     visitor->trace(m_item);
 }
 
 } // namespace blink