Use enum class for subtypes of CPDF_Annot.

core/fpdfdoc/cpdf_annotlist.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 "core/fpdfdoc/include/cpdf_annotlist.h"
 
 #include "core/fpdfapi/fpdf_page/include/cpdf_page.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_document.h"
@@ skipping 92 matching lines @@
 
 void CPDF_AnnotList::DisplayPass(CPDF_Page* pPage,
                                  CFX_RenderDevice* pDevice,
                                  CPDF_RenderContext* pContext,
                                  FX_BOOL bPrinting,
                                  CFX_Matrix* pMatrix,
                                  FX_BOOL bWidgetPass,
                                  CPDF_RenderOptions* pOptions,
                                  FX_RECT* clip_rect) {
   for (const auto& pAnnot : m_AnnotList) {
-    bool bWidget = pAnnot->GetSubtype() == "Widget";
+    bool bWidget = pAnnot->GetSubtype() == CPDF_Annot::Subtype::WIDGET;
     if ((bWidgetPass && !bWidget) || (!bWidgetPass && bWidget))
       continue;
 
     uint32_t annot_flags = pAnnot->GetFlags();
     if (annot_flags & ANNOTFLAG_HIDDEN)
       continue;
 
     if (bPrinting && (annot_flags & ANNOTFLAG_PRINT) == 0)
       continue;
 
@@ skipping 49 matching lines @@
                                    CPDF_RenderContext* pContext,
                                    FX_BOOL bPrinting,
                                    CFX_Matrix* pMatrix,
                                    FX_BOOL bShowWidget,
                                    CPDF_RenderOptions* pOptions) {
   uint32_t dwAnnotFlags = bShowWidget ? ANNOTFLAG_INVISIBLE | ANNOTFLAG_HIDDEN
                                       : ANNOTFLAG_INVISIBLE;
   DisplayAnnots(pPage, nullptr, pContext, bPrinting, pMatrix, dwAnnotFlags,
                 pOptions, nullptr);
 }