Replace FX_SAFE_STRSIZE with FX_SAFE_SIZE_T

BUG=pdfium:828

Change-Id: If9560338c456b28f968e743a90a3629791d87df0
Reviewed-on: https://pdfium-review.googlesource.com/14832
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>

testing/libfuzzer/pdf_xml_fuzzer.cc

diff --git a/testing/libfuzzer/pdf_xml_fuzzer.cc b/testing/libfuzzer/pdf_xml_fuzzer.cc
index 0c3cf4f..d8010f9 100644
--- a/testing/libfuzzer/pdf_xml_fuzzer.cc
+++ b/testing/libfuzzer/pdf_xml_fuzzer.cc
@@ -46,7 +46,7 @@
 }  // namespace
 
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
-  FX_SAFE_STRSIZE safe_size = size;
+  FX_SAFE_SIZE_T safe_size = size;
   if (!safe_size.IsValid())
     return 0;