Consistently pass FPDF handles by value.

Change-Id: I1b31217c756620873f59527768464aec02a82900
Reviewed-on: https://pdfium-review.googlesource.com/6677
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
diff --git a/samples/pdfium_test.cc b/samples/pdfium_test.cc
index 5520fa4..86f6f89 100644
--- a/samples/pdfium_test.cc
+++ b/samples/pdfium_test.cc
@@ -755,8 +755,8 @@
 
 void Add_Segment(FX_DOWNLOADHINTS* hints, size_t offset, size_t size) {}
 
-void SendPageEvents(const FPDF_FORMHANDLE& form,
-                    const FPDF_PAGE& page,
+void SendPageEvents(FPDF_FORMHANDLE form,
+                    FPDF_PAGE page,
                     const std::string& events) {
   auto lines = StringSplit(events, '\n');
   for (auto line : lines) {