Fix the code which causes Windows GN build warning

core/fxge/ge/fx_ge_fontmap.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 <algorithm>
 #include <limits>
 #include <vector>
 
@@ skipping 1138 matching lines @@
         pSubstFont->m_SubstFlags |= FXFONT_SUBST_NONSYMBOL;
         return FindSubstFont(family, bTrueType, flags & ~FXFONT_SYMBOLIC,
                              weight, italic_angle, 0, pSubstFont);
       }
       if (Charset == FXFONT_ANSI_CHARSET) {
         pSubstFont->m_SubstFlags |= FXFONT_SUBST_STANDARD;
         return UseInternalSubst(pSubstFont, iBaseFont, italic_angle, old_weight,
                                 PitchFamily);
       }
 
-      auto it = std::find_if(
-          m_FaceArray.begin(), m_FaceArray.end(),
-          [Charset](const FaceData& face) { return face.charset == Charset; });
+      auto it =
+          std::find_if(m_FaceArray.begin(), m_FaceArray.end(),
+                       [Charset](const FaceData& face) {
+                         return face.charset == static_cast<uint32_t>(Charset);
+                       });
       if (it == m_FaceArray.end()) {
         return UseInternalSubst(pSubstFont, iBaseFont, italic_angle, old_weight,
                                 PitchFamily);
       }
       hFont = m_pFontInfo->GetFont(it->name);
     }
   }
   pSubstFont->m_ExtHandle = m_pFontInfo->RetainFont(hFont);
   if (!hFont)
     return nullptr;
@@ skipping 470 matching lines @@
 int PDF_GetStandardFontName(CFX_ByteString* name) {
   AltFontName* found = static_cast<AltFontName*>(
       FXSYS_bsearch(name->c_str(), g_AltFontNames, FX_ArraySize(g_AltFontNames),
                     sizeof(AltFontName), CompareString));
   if (!found)
     return -1;
 
   *name = g_Base14FontNames[found->m_Index];
   return found->m_Index;
 }