Remove the Element.prefix setter

Source/core/dom/Attribute.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2008, 2012 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
@@ skipping 36 matching lines @@
     const AtomicString& prefix() const { return m_name.prefix(); }
     const AtomicString& localName() const { return m_name.localName(); }
     const AtomicString& namespaceURI() const { return m_name.namespaceURI(); }
 
     const QualifiedName& name() const { return m_name; }
 
     bool isEmpty() const { return m_value.isEmpty(); }
     bool matches(const QualifiedName&) const;
 
     void setValue(const AtomicString& value) { m_value = value; }
-    void setPrefix(const AtomicString& prefix) { m_name.setPrefix(prefix); }
 
     // Note: This API is only for HTMLTreeBuilder.  It is not safe to change the
     // name of an attribute once parseAttribute has been called as DOM
     // elements may have placed the Attribute in a hash by name.
     void parserSetName(const QualifiedName& name) { m_name = name; }
 
 #if COMPILER(MSVC)
     // NOTE: This constructor is not actually implemented, it's just defined so MSVC
     // will let us use a zero-length array of Attributes.
     Attribute();
 #endif
 
 private:
     QualifiedName m_name;
     AtomicString m_value;
 };
 
 inline bool Attribute::matches(const QualifiedName& qualifiedName) const
 {
     if (qualifiedName.localName() != localName())
         return false;
     return qualifiedName.prefix() == starAtom || qualifiedName.namespaceURI() == namespaceURI();
 }
 
 } // namespace blink
 
 #endif // Attribute_h