Fix include in pdf_fuzzer_init_public.cc.

Turns out it needs <string> and <string.h>. GCC complained about the
lack of <string.h>.

Change-Id: I30749eca41e991051def2901a261525db4207e66
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/82018
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/testing/fuzzers/pdf_fuzzer_init_public.cc b/testing/fuzzers/pdf_fuzzer_init_public.cc
index a374167..5fc463d 100644
--- a/testing/fuzzers/pdf_fuzzer_init_public.cc
+++ b/testing/fuzzers/pdf_fuzzer_init_public.cc
@@ -4,6 +4,8 @@
 
 #include "testing/fuzzers/pdf_fuzzer_init_public.h"
 
+#include <string.h>  // For memset()
+
 #include <string>
 
 #include "testing/fuzzers/pdfium_fuzzer_util.h"