Use glyph index as backup of ExtGID on Mac

core/fxge/apple/fx_apple_platform.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 "core/fxcrt/fx_system.h"
 
 #if _FXM_PLATFORM_ == _FXM_PLATFORM_APPLE_
 
@@ skipping 45 matching lines @@
       return FALSE;
 
     pFont->SetPlatformFont(
         quartz2d.CreateFont(pFont->GetFontData(), pFont->GetSize()));
     if (!pFont->GetPlatformFont())
       return FALSE;
   }
   CFX_FixedBufGrow<uint16_t, 32> glyph_indices(nChars);
   CFX_FixedBufGrow<CGPoint, 32> glyph_positions(nChars);
   for (int i = 0; i < nChars; i++) {
-    glyph_indices[i] = pCharPos[i].m_ExtGID;
+    glyph_indices[i] =
+        pCharPos[i].m_ExtGID ? pCharPos[i].m_ExtGID : pCharPos[i].m_GlyphIndex;
     if (bNegSize)
       glyph_positions[i].x = -pCharPos[i].m_OriginX;
     else
       glyph_positions[i].x = pCharPos[i].m_OriginX;
     glyph_positions[i].y = pCharPos[i].m_OriginY;
   }
   if (bNegSize) {
     new_matrix.a = -new_matrix.a;
     new_matrix.c = -new_matrix.c;
   } else {
@@ skipping 103 matching lines @@
   if (m_pPlatformFont) {
     CQuartz2D& quartz2d =
         static_cast<CApplePlatform*>(CFX_GEModule::Get()->GetPlatformData())
             ->m_quartz2d;
     quartz2d.DestroyFont(m_pPlatformFont);
     m_pPlatformFont = nullptr;
   }
 }
 
 #endif  // _FXM_PLATFORM_  == _FXM_PLATFORM_APPLE_