Re-enable several MSVC warnings

core/fxge/ge/fx_ge_font.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/fxge/ge/fx_text_int.h"
 #include "core/include/fxge/fx_freetype.h"
 #include "core/include/fxge/fx_ge.h"
 
@@ skipping 504 matching lines @@
   FXFT_Face face = m_pFont->GetFace();
   int nmaps = FXFT_Get_Face_CharmapCount(face);
   for (int i = 0; i < nmaps; i++) {
     int nEncodingID =
         FXFT_Get_Charmap_Encoding(FXFT_Get_Face_Charmaps(face)[i]);
     if (nEncodingID == FXFM_ENCODING_UNICODE ||
         nEncodingID == FXFM_ENCODING_MS_SYMBOL) {
       return Unicode;
     }
   }
-  return -1;
+  return static_cast<FX_DWORD>(-1);
 }
 
 CFX_UnicodeEncodingEx* FX_CreateFontEncodingEx(CFX_Font* pFont,
                                                FX_DWORD nEncodingID) {
   if (!pFont || !pFont->GetFace())
     return nullptr;
 
   if (nEncodingID != FXFM_ENCODING_NONE)
     return _FXFM_CreateFontEncoding(pFont, nEncodingID);
 
   for (size_t i = 0; i < FX_ArraySize(g_EncodingID); ++i) {
     CFX_UnicodeEncodingEx* pFontEncoding =
         _FXFM_CreateFontEncoding(pFont, g_EncodingID[i]);
     if (pFontEncoding) {
       return pFontEncoding;
     }
   }
   return NULL;
 }
 #endif  // PDF_ENABLE_XFA