Code change to avoid signed/unsigned mismatch warnings

fpdfsdk/fpdfview.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 "public/fpdfview.h"
 
 #include <memory>
 
@@ skipping 176 matching lines @@
 
 FX_BOOL CPDF_CustomAccess::ReadBlock(void* buffer,
                                      FX_FILESIZE offset,
                                      size_t size) {
   if (offset < 0) {
     return FALSE;
   }
   FX_SAFE_FILESIZE newPos =
       pdfium::base::checked_cast<FX_FILESIZE, size_t>(size);
   newPos += offset;
-  if (!newPos.IsValid() || newPos.ValueOrDie() > m_FileAccess.m_FileLen) {
+  if (!newPos.IsValid() ||
+      newPos.ValueOrDie() > static_cast<FX_FILESIZE>(m_FileAccess.m_FileLen)) {
     return FALSE;
   }
   return m_FileAccess.m_GetBlock(m_FileAccess.m_Param, offset, (uint8_t*)buffer,
                                  size);
 }
 
 // 0 bit: FPDF_POLICY_MACHINETIME_ACCESS
 static uint32_t foxit_sandbox_policy = 0xFFFFFFFF;
 
 void FSDK_SetSandBoxPolicy(FPDF_DWORD policy, FPDF_BOOL enable) {
@@ skipping 950 matching lines @@
   if (!buffer) {
     *buflen = len;
   } else if (*buflen >= len) {
     memcpy(buffer, utf16Name.c_str(), len);
     *buflen = len;
   } else {
     *buflen = -1;
   }
   return (FPDF_DEST)pDestObj;
 }