Get rid of custom code for clipboard.clearData()

Source/core/dom/Clipboard.h

 /*
  * Copyright (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2001 Tobias Anton (anton@stud.fbi.fh-darmstadt.de)
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2008 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 49 matching lines @@
 
     bool isForCopyAndPaste() const { return m_clipboardType == CopyAndPaste; }
     bool isForDragAndDrop() const { return m_clipboardType == DragAndDrop; }
 
     String dropEffect() const { return dropEffectIsUninitialized() ? "none" : m_dropEffect; }
     void setDropEffect(const String&);
     bool dropEffectIsUninitialized() const { return m_dropEffect == "uninitialized"; }
     String effectAllowed() const { return m_effectAllowed; }
     void setEffectAllowed(const String&);
 
-    void clearData(const String& type);
-    void clearAllData();
+    void clearData(const String& type = String());
     String getData(const String& type) const;
     bool setData(const String& type, const String& data);
 
     // extensions beyond IE's API
     Vector<String> types() const;
     PassRefPtr<FileList> files() const;
 
     IntPoint dragLocation() const { return m_dragLoc; }
     ImageResource* dragImage() const { return m_dragImage.get(); }
     void setDragImage(ImageResource*, const IntPoint&);
@@ skipping 48 matching lines @@
     ResourcePtr<ImageResource> m_dragImage;
     RefPtr<Node> m_dragImageElement;
 };
 
 DragOperation convertDropZoneOperationToDragOperation(const String& dragOperation);
 String convertDragOperationToDropZoneOperation(DragOperation);
 
 } // namespace WebCore
 
 #endif // Clipboard_h