Remove fgas_base.h and IWYU

xfa/src/fgas/src/crt/fx_system.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 "xfa/src/fgas/src/fgas_base.h"
+#include "core/include/fxcrt/fx_system.h"
+
 #if _FX_OS_ == _FX_WIN32_DESKTOP_ || _FX_OS_ == _FX_WIN32_MOBILE_ || \
     _FX_OS_ == _FX_WIN64_
 #include <io.h>
 #elif _FX_OS_ == _FX_LINUX_DESKTOP_ || _FX_OS_ == _FX_LINUX_Mini_
 #include <sys/times.h>
 #endif
 
 namespace {
 
 inline FX_BOOL FX_isupper(int32_t ch) {
@@ skipping 85 matching lines @@
       } else {
         break;
       }
     }
   }
   if (pUsedLen) {
     *pUsedLen = iUsedLen;
   }
   return bNegtive ? -fValue : fValue;
 }