flag to use const& instead of const* for src-rect

gm/bitmaprecttest.cpp

Index: gm/bitmaprecttest.cpp
diff --git a/gm/bitmaprecttest.cpp b/gm/bitmaprecttest.cpp
index 630c90c600d6d8530ee5cccee693a8d3cf1dc6f1..878029a8dd7d750434ca7ac70008e1cebdcf1714 100644
--- a/gm/bitmaprecttest.cpp
+++ b/gm/bitmaprecttest.cpp
@@ -43,7 +43,7 @@ static void test_bitmaprect(SkCanvas* canvas) {
     SkScalar scale = 0.472560018f;
     canvas->save();
     canvas->scale(scale, scale);
-    canvas->drawBitmapRect(bm, SkRect::MakeXYWH(100, 100, 128, 128));
+    canvas->drawBitmapRect(bm, SkRect::MakeXYWH(100, 100, 128, 128), nullptr);
     canvas->restore();
 
     canvas->scale(-1, 1);