return pictures as sk_sp

bench/PictureOverheadBench.cpp

Index: bench/PictureOverheadBench.cpp
diff --git a/bench/PictureOverheadBench.cpp b/bench/PictureOverheadBench.cpp
index 62a51ec3598d05a8a2b13c48db8d01dff1dbebac..fc72f8623add9f9946803bed1c5da1a3d91b18e7 100644
--- a/bench/PictureOverheadBench.cpp
+++ b/bench/PictureOverheadBench.cpp
@@ -26,7 +26,7 @@ struct PictureOverheadBench : public Benchmark {
             if (kDraw) {
                 rec.getRecordingCanvas()->drawRect(SkRect::MakeXYWH(10, 10, 1000, 1000), SkPaint());
             }
-            SkAutoTUnref<SkPicture> pic(rec.endRecordingAsPicture());
+            (void)rec.finishRecordingAsPicture();
         }
     }
 };