Return size_t from ParseTimeZone().

One of the last usages of int32_t for sizes in cfgas_formatstring.cpp

Change-Id: I5b672d21e69893bbff12345c3f71bfb42421dc88
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/51750
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/xfa/fgas/crt/cfgas_formatstring.cpp b/xfa/fgas/crt/cfgas_formatstring.cpp
index d30fa7b..7dccda0 100644
--- a/xfa/fgas/crt/cfgas_formatstring.cpp
+++ b/xfa/fgas/crt/cfgas_formatstring.cpp
@@ -78,7 +78,7 @@
 const wchar_t gs_wsDateSymbols[] = L"DJMEeGgYwW";
 const wchar_t gs_wsConstChars[] = L",-:/. ";
 
-int32_t ParseTimeZone(pdfium::span<const wchar_t> pStr, FX_TIMEZONE* tz) {
+size_t ParseTimeZone(pdfium::span<const wchar_t> pStr, FX_TIMEZONE* tz) {
   tz->tzHour = 0;
   tz->tzMinute = 0;
   if (pStr.empty())