Fix IWYU errors in pdfium_test_write_helper.cc.

Change-Id: I39bafa0d3cb750f3b735592c8d2d96650c7267ae
Reviewed-on: https://pdfium-review.googlesource.com/29110
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/samples/pdfium_test_write_helper.cc b/samples/pdfium_test_write_helper.cc
index 27f43a6..a323658 100644
--- a/samples/pdfium_test_write_helper.cc
+++ b/samples/pdfium_test_write_helper.cc
@@ -4,6 +4,9 @@
 
 #include "samples/pdfium_test_write_helper.h"
 
+#include <memory>
+#include <vector>
+
 #include "public/cpp/fpdf_deleters.h"
 #include "public/fpdf_annot.h"
 #include "public/fpdf_attachment.h"