Fix a bunch of sign mismatch warnings.

core/src/fpdfapi/fpdf_render/fpdf_render_loadimage.cpp

Index: core/src/fpdfapi/fpdf_render/fpdf_render_loadimage.cpp
diff --git a/core/src/fpdfapi/fpdf_render/fpdf_render_loadimage.cpp b/core/src/fpdfapi/fpdf_render/fpdf_render_loadimage.cpp
index 0362ff2e90cc48eea7fbc99f4eb80dc1b32f83e2..c4b4f703817ac305428cd859a664af0c8a46cba9 100644
--- a/core/src/fpdfapi/fpdf_render/fpdf_render_loadimage.cpp
+++ b/core/src/fpdfapi/fpdf_render/fpdf_render_loadimage.cpp
@@ -748,7 +748,7 @@ void CPDF_DIBSource::LoadJpxBitmap() {
   }
   m_pCachedBitmap->Clear(0xFFFFFFFF);
   context->set_output_offsets(FX_Alloc(uint8_t, components));
-  for (int i = 0; i < components; ++i)
+  for (FX_DWORD i = 0; i < components; ++i)
     context->output_offsets()[i] = i;
   if (bSwapRGB) {
     context->output_offsets()[0] = 2;
@@ -1492,7 +1492,7 @@ void CPDF_DIBSource::DownSampleScanline32Bit(int orig_Bpp,
                                               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]) *