Reduce signed/unsigned comparison warnings

fpdfsdk/pdfwindow/PWL_FontMap.cpp

Index: fpdfsdk/pdfwindow/PWL_FontMap.cpp
diff --git a/fpdfsdk/pdfwindow/PWL_FontMap.cpp b/fpdfsdk/pdfwindow/PWL_FontMap.cpp
index 0a5eef6b19268a860b05c328324d1c8e3fa1b9c7..3f149e7193ae0af559696ebfc04743fedefbe312 100644
--- a/fpdfsdk/pdfwindow/PWL_FontMap.cpp
+++ b/fpdfsdk/pdfwindow/PWL_FontMap.cpp
@@ -177,7 +177,7 @@ void CPWL_FontMap::Initialize() {
 }
 
 FX_BOOL CPWL_FontMap::IsStandardFont(const CFX_ByteString& sFontName) {
-  for (int32_t i = 0; i < FX_ArraySize(g_sDEStandardFontName); ++i) {
+  for (size_t i = 0; i < FX_ArraySize(g_sDEStandardFontName); ++i) {
     if (sFontName == g_sDEStandardFontName[i])
       return TRUE;
   }