Fix compile on mac: format string mismatch error.

samples/pdfium_test.cc

Index: samples/pdfium_test.cc
diff --git a/samples/pdfium_test.cc b/samples/pdfium_test.cc
index 7436e9d86cccbd00e834b2b9f79deae908da832a..0f0c875f3d95ffb8309e6dac175d06d2b8884d0a 100644
--- a/samples/pdfium_test.cc
+++ b/samples/pdfium_test.cc
@@ -359,8 +359,8 @@ void RenderPdf(const char* name, const char* pBuf, size_t len,
   FPDF_CloseDocument(doc);
   FPDFAvail_Destroy(pdf_avail);
 
-  printf("Loaded, parsed and rendered %d pages.\n", rendered_pages);
-  printf("Skipped %d bad pages.\n", bad_pages);
+  printf("Loaded, parsed and rendered %zu pages.\n", rendered_pages);
+  printf("Skipped %zu bad pages.\n", bad_pages);
 }
 
 int main(int argc, const char* argv[]) {