Review and cleanup lint warnings.

fpdfsdk/src/pdfwindow/PWL_ListBox.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "fpdfsdk/include/pdfwindow/PWL_ListBox.h"
 
+#include <string>
+
 #include "fpdfsdk/include/pdfwindow/PWL_Edit.h"
 #include "fpdfsdk/include/pdfwindow/PWL_EditCtrl.h"
 #include "fpdfsdk/include/pdfwindow/PWL_ScrollBar.h"
 #include "fpdfsdk/include/pdfwindow/PWL_Utils.h"
 #include "fpdfsdk/include/pdfwindow/PWL_Wnd.h"
 #include "public/fpdf_fwlevent.h"
 
 #define IsFloatZero(f) ((f) < 0.0001 && (f) > -0.0001)
 #define IsFloatBigger(fa, fb) ((fa) > (fb) && !IsFloatZero((fa) - (fb)))
 #define IsFloatSmaller(fa, fb) ((fa) < (fb) && !IsFloatZero((fa) - (fb)))
@@ skipping 505 matching lines @@
   if (zDelta < 0) {
     m_pList->OnVK_DOWN(IsSHIFTpressed(nFlag), IsCTRLpressed(nFlag));
   } else {
     m_pList->OnVK_UP(IsSHIFTpressed(nFlag), IsCTRLpressed(nFlag));
   }
 
   FX_BOOL bExit = FALSE;
   OnNotifySelChanged(FALSE, bExit, nFlag);
   return TRUE;
 }