Switch from _DEBUG to NDEBUG.

core/src/fxcrt/fx_basic_wstring.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 <stddef.h>  // For offsetof().
 
 #include <algorithm>
 #include <cctype>
 
 #include "core/include/fxcrt/fx_basic.h"
 #include "core/include/fxcrt/fx_ext.h"
 #include "third_party/base/numerics/safe_math.h"
 
 namespace {
 
-#if defined(_DEBUG)
+#ifndef NDEBUG
 bool IsValidCodePage(FX_WORD codepage) {
   switch (codepage) {
     case 0:
     case 932:
     case 936:
     case 949:
     case 950:
       return true;
 
     default:
@@ skipping 1013 matching lines @@
   int dest_len =
       FXSYS_MultiByteToWideChar(codepage, 0, bstr, src_len, nullptr, 0);
   CFX_WideString wstr;
   if (dest_len) {
     FX_WCHAR* dest_buf = wstr.GetBuffer(dest_len);
     FXSYS_MultiByteToWideChar(codepage, 0, bstr, src_len, dest_buf, dest_len);
     wstr.ReleaseBuffer(dest_len);
   }
   return wstr;
 }