Re-enable several MSVC warnings

core/fxcodec/codec/fx_codec_tiff.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/fxcodec/codec/codec_int.h"
 #include "core/include/fxcodec/fx_codec.h"
 #include "core/include/fxge/fx_dib.h"
 
@@ skipping 104 matching lines @@
   switch (whence) {
     case 0:
       pTiffContext->offset = (FX_DWORD)offset;
       break;
     case 1:
       pTiffContext->offset += (FX_DWORD)offset;
       break;
     case 2:
       if (pTiffContext->isDecoder) {
         if (pTiffContext->io.in->GetSize() < (FX_FILESIZE)offset) {
-          return -1;
+          return static_cast<toff_t>(-1);
         }
         pTiffContext->offset =
             (FX_DWORD)(pTiffContext->io.in->GetSize() - offset);
       } else {
         if (pTiffContext->io.out->GetSize() < (FX_FILESIZE)offset) {
-          return -1;
+          return static_cast<toff_t>(-1);
         }
         pTiffContext->offset =
             (FX_DWORD)(pTiffContext->io.out->GetSize() - offset);
       }
       break;
     default:
-      return -1;
+      return static_cast<toff_t>(-1);
   }
   ASSERT(pTiffContext->isDecoder ? (pTiffContext->offset <=
                                     (FX_DWORD)pTiffContext->io.in->GetSize())
                                  : TRUE);
   return pTiffContext->offset;
 }
 static int _tiff_close(thandle_t context) {
   return 0;
 }
 static toff_t _tiff_get_size(thandle_t context) {
@@ skipping 386 matching lines @@
   return pDecoder->LoadFrameInfo(frame, width, height, comps, bpc, pAttribute);
 }
 FX_BOOL CCodec_TiffModule::Decode(void* ctx, class CFX_DIBitmap* pDIBitmap) {
   CCodec_TiffContext* pDecoder = (CCodec_TiffContext*)ctx;
   return pDecoder->Decode(pDIBitmap);
 }
 void CCodec_TiffModule::DestroyDecoder(void* ctx) {
   CCodec_TiffContext* pDecoder = (CCodec_TiffContext*)ctx;
   delete pDecoder;
 }