return pictures as sk_sp

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1811703002

Review URL: https://codereview.chromium.org/1811703002
diff --git a/bench/PicturePlaybackBench.cpp b/bench/PicturePlaybackBench.cpp
index 84951a1..2b2b6ad 100644
--- a/bench/PicturePlaybackBench.cpp
+++ b/bench/PicturePlaybackBench.cpp
@@ -42,7 +42,7 @@
         SkPictureRecorder recorder;
         SkCanvas* pCanvas = recorder.beginRecording(PICTURE_WIDTH, PICTURE_HEIGHT, nullptr, 0);
         this->recordCanvas(pCanvas);
-        SkAutoTUnref<SkPicture> picture(recorder.endRecording());
+        sk_sp<SkPicture> picture(recorder.finishRecordingAsPicture());
 
         const SkPoint translateDelta = getTranslateDelta(loops);
 
@@ -182,7 +182,7 @@
                 paint.setAlpha(0xFF);
                 canvas->drawRect(SkRect::MakeXYWH(x,y,w,h), paint);
             }
-        fPic.reset(recorder.endRecording());
+        fPic = recorder.finishRecordingAsPicture();
     }
 
     void onDraw(int loops, SkCanvas* canvas) override {
@@ -207,10 +207,10 @@
     }
 
 private:
-    BBH                     fBBH;
-    Mode                    fMode;
-    SkString                fName;
-    SkAutoTUnref<SkPicture> fPic;
+    BBH                 fBBH;
+    Mode                fMode;
+    SkString            fName;
+    sk_sp<SkPicture>    fPic;
 };
 
 DEF_BENCH( return new TiledPlaybackBench(kNone,     kRandom); )