Fix a bunch of sign mismatch warnings.

core/src/fpdfapi/fpdf_render/fpdf_render_loadimage.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 <vector>
 
 #include "../../../../third_party/base/nonstd_unique_ptr.h"
 #include "../../../include/fpdfapi/fpdf_module.h"
@@ skipping 720 matching lines @@
     format = FXDIB_Rgb;
   }
 
   m_pCachedBitmap.reset(new CFX_DIBitmap);
   if (!m_pCachedBitmap->Create(width, height, format)) {
     m_pCachedBitmap.reset();
     return;
   }
   m_pCachedBitmap->Clear(0xFFFFFFFF);
   std::vector<uint8_t> output_offsets(components);
-  for (int i = 0; i < components; ++i)
+  for (FX_DWORD i = 0; i < components; ++i)
     output_offsets[i] = i;
   if (bSwapRGB) {
     output_offsets[0] = 2;
     output_offsets[2] = 0;
   }
   if (!pJpxModule->Decode(context->decoder(), m_pCachedBitmap->GetBuffer(),
                           m_pCachedBitmap->GetPitch(), output_offsets)) {
     m_pCachedBitmap.reset();
     return;
   }
@@ skipping 725 matching lines @@
               temp[j] = (uint8_t)(_GetBits8(pSrcPixel, src_bit_pos, m_bpc) *
                                   unit_To8Bpc);
               src_bit_pos += m_bpc;
             }
             m_pColorSpace->TranslateImageLine(color, temp, 1, 0, 0, bTransMask);
           } else {
             m_pColorSpace->TranslateImageLine(color, pSrcPixel, 1, 0, 0,
                                               bTransMask);
           }
         } else {
-          for (int j = 0; j < m_nComponents; ++j) {
+          for (FX_DWORD j = 0; j < m_nComponents; ++j) {
             int color_value =
                 (int)((m_pCompData[j].m_DecodeMin +
                        m_pCompData[j].m_DecodeStep * (FX_FLOAT)pSrcPixel[j]) *
                           255.0f +
                       0.5f);
             temp[j] =
                 color_value > 255 ? 255 : (color_value < 0 ? 0 : color_value);
           }
           m_pColorSpace->TranslateImageLine(color, temp, 1, 0, 0, bTransMask);
         }
@@ skipping 157 matching lines @@
 }
 FX_BOOL CPDF_ImageLoader::Continue(void* LoadHandle, IFX_Pause* pPause) {
   return ((CPDF_ProgressiveImageLoaderHandle*)LoadHandle)->Continue(pPause);
 }
 CPDF_ImageLoader::~CPDF_ImageLoader() {
   if (!m_bCached) {
     delete m_pBitmap;
     delete m_pMask;
   }
 }