Use enum class for subtypes of CPDF_Annot.

fpdfsdk/include/cba_annotiterator.h

 // Copyright 2016 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
 
 #ifndef FPDFSDK_INCLUDE_CBA_ANNOTITERATOR_H_
 #define FPDFSDK_INCLUDE_CBA_ANNOTITERATOR_H_
 
 #include <vector>
 
+#include "core/fpdfdoc/include/cpdf_annot.h"
 #include "core/fxcrt/include/fx_coordinates.h"
 #include "core/fxcrt/include/fx_string.h"
 
 class CPDFSDK_Annot;
 class CPDFSDK_PageView;
 
 class CBA_AnnotIterator {
  public:
   enum TabOrder { STRUCTURE = 0, ROW, COLUMN };
 
   CBA_AnnotIterator(CPDFSDK_PageView* pPageView,
-                    const CFX_ByteString& sAnnotSubtype);
+                    CPDF_Annot::Subtype nAnnotSubtype);
   ~CBA_AnnotIterator();
 
   CPDFSDK_Annot* GetFirstAnnot();
   CPDFSDK_Annot* GetLastAnnot();
   CPDFSDK_Annot* GetNextAnnot(CPDFSDK_Annot* pAnnot);
   CPDFSDK_Annot* GetPrevAnnot(CPDFSDK_Annot* pAnnot);
 
  private:
   void GenerateResults();
   static CFX_FloatRect GetAnnotRect(const CPDFSDK_Annot* pAnnot);
 
   // Function signature compatible with std::sort().
   static bool CompareByLeftAscending(const CPDFSDK_Annot* p1,
                                      const CPDFSDK_Annot* p2);
   static bool CompareByTopDescending(const CPDFSDK_Annot* p1,
                                      const CPDFSDK_Annot* p2);
 
   TabOrder m_eTabOrder;
   CPDFSDK_PageView* m_pPageView;
-  CFX_ByteString m_sAnnotSubtype;
+  CPDF_Annot::Subtype m_nAnnotSubtype;
   std::vector<CPDFSDK_Annot*> m_Annots;
 };
 
 #endif  // FPDFSDK_INCLUDE_CBA_ANNOTITERATOR_H_