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

BUG=skia:

Review URL: https://codereview.chromium.org/1272713005
diff --git a/src/utils/SkNWayCanvas.cpp b/src/utils/SkNWayCanvas.cpp
index 0efc98c..fb8d0ee 100644
--- a/src/utils/SkNWayCanvas.cpp
+++ b/src/utils/SkNWayCanvas.cpp
@@ -196,7 +196,7 @@
                                     const SkPaint* paint, SrcRectConstraint constraint) {
     Iter iter(fList);
     while (iter.next()) {
-        iter->drawBitmapRect(bitmap, src, dst, paint, (SrcRectConstraint)constraint);
+        iter->legacy_drawBitmapRect(bitmap, src, dst, paint, (SrcRectConstraint)constraint);
     }
 }
 
@@ -220,7 +220,7 @@
                                    const SkPaint* paint, SrcRectConstraint constraint) {
     Iter iter(fList);
     while (iter.next()) {
-        iter->drawImageRect(image, src, dst, paint, constraint);
+        iter->legacy_drawImageRect(image, src, dst, paint, constraint);
     }
 }