Remove unused includes from core/{editing,fileapi,history,html}

Source/core/html/parser/HTMLSourceTracker.h

 /*
  * Copyright (C) 2010 Adam Barth. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 10 matching lines @@
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef HTMLSourceTracker_h
 #define HTMLSourceTracker_h
 
 #include "core/html/parser/HTMLToken.h"
 #include "core/platform/text/SegmentedString.h"
-#include <wtf/text/StringBuilder.h>
 
 namespace WebCore {
 
 class HTMLTokenizer;
 
 class HTMLSourceTracker {
     WTF_MAKE_NONCOPYABLE(HTMLSourceTracker);
 public:
     HTMLSourceTracker();
 
     // FIXME: Once we move "end" into HTMLTokenizer, rename "start" to
     // something that makes it obvious that this method can be called multiple
     // times.
     void start(SegmentedString&, HTMLTokenizer*, HTMLToken&);
     void end(SegmentedString&, HTMLTokenizer*, HTMLToken&);
 
     String sourceForToken(const HTMLToken&);
 
 private:
     SegmentedString m_previousSource;
     SegmentedString m_currentSource;
 
     String m_cachedSourceForToken;
 };
 
 }
 
 #endif