core: Include wtf files using "wtf/foo.h" form.

Source/core/xml/XMLSerializer.cpp

 /*
  *  Copyright (C) 2003, 2006 Apple Inc. All rights reserved.
  *  Copyright (C) 2006 Samuel Weinig (sam@webkit.org)
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  *  Lesser General Public License for more details.
  *
  *  You should have received a copy of the GNU Lesser General Public
  *  License along with this library; if not, write to the Free Software
  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
 #include "config.h"
 #include "core/xml/XMLSerializer.h"
 
 #include "bindings/v8/ExceptionState.h"
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/editing/markup.h"
-#include <wtf/text/WTFString.h>
+#include "wtf/text/WTFString.h"
 
 namespace WebCore {
 
 String XMLSerializer::serializeToString(Node* node, ExceptionState& es)
 {
     if (!node)
         return String();
 
     if (!node->document()) {
         // Due to the fact that DocumentType nodes are created by the DOMImplementation
         // and not the Document, it is possible for it to not have a Document associated
         // with it.  It should be the only type of node where this is possible.
         ASSERT(node->nodeType() == Node::DOCUMENT_TYPE_NODE);
 
         es.throwDOMException(InvalidAccessError);
         return String();
     }
 
     return createMarkup(node);
 }
 
 } // namespace WebCore