Use enum class for subtypes of CPDF_Annot.

fpdfsdk/cpdfsdk_baannot.cpp

 // 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
 
 #include "fpdfsdk/include/cpdfsdk_baannot.h"
 
 #include "core/fpdfapi/fpdf_parser/include/cpdf_array.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_number.h"
@@ skipping 24 matching lines @@
   ASSERT(rect.right - rect.left >= GetMinWidth());
   ASSERT(rect.top - rect.bottom >= GetMinHeight());
 
   m_pAnnot->GetAnnotDict()->SetAtRect("Rect", rect);
 }
 
 CFX_FloatRect CPDFSDK_BAAnnot::GetRect() const {
   return m_pAnnot->GetRect();
 }
 
-CFX_ByteString CPDFSDK_BAAnnot::GetAnnotSubtype() const {
+CPDF_Annot::Subtype CPDFSDK_BAAnnot::GetAnnotSubtype() const {
   return m_pAnnot->GetSubtype();
 }
 
 void CPDFSDK_BAAnnot::DrawAppearance(CFX_RenderDevice* pDevice,
                                      const CFX_Matrix* pUser2Device,
                                      CPDF_Annot::AppearanceMode mode,
                                      const CPDF_RenderOptions* pOptions) {
   m_pAnnot->DrawAppearance(m_pPageView->GetPDFPage(), pDevice, pUser2Device,
                            mode, pOptions);
 }
@@ skipping 342 matching lines @@
                                    CPDF_RenderOptions* pOptions) {
   m_pAnnot->GetAPForm(m_pPageView->GetPDFPage(), CPDF_Annot::Normal);
   m_pAnnot->DrawAppearance(m_pPageView->GetPDFPage(), pDevice, pUser2Device,
                            CPDF_Annot::Normal, nullptr);
 }
 
 void CPDFSDK_BAAnnot::SetOpenState(bool bOpenState) {
   if (CPDF_Annot* pAnnot = m_pAnnot->GetPopupAnnot())
     pAnnot->SetOpenState(bOpenState);
 }