change flattenable factory to return sk_sp

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1855733002

Review URL: https://codereview.chromium.org/1855733002
diff --git a/src/effects/SkPictureImageFilter.cpp b/src/effects/SkPictureImageFilter.cpp
index 2005463..2dff41a 100644
--- a/src/effects/SkPictureImageFilter.cpp
+++ b/src/effects/SkPictureImageFilter.cpp
@@ -31,7 +31,7 @@
     , fFilterQuality(filterQuality) {
 }
 
-SkFlattenable* SkPictureImageFilter::CreateProc(SkReadBuffer& buffer) {
+sk_sp<SkFlattenable> SkPictureImageFilter::CreateProc(SkReadBuffer& buffer) {
     sk_sp<SkPicture> picture;
     SkRect cropRect;
 
@@ -58,9 +58,9 @@
         } else {
             filterQuality = (SkFilterQuality)buffer.readInt();
         }
-        return MakeForLocalSpace(picture, cropRect, filterQuality).release();
+        return MakeForLocalSpace(picture, cropRect, filterQuality);
     }
-    return Make(picture, cropRect).release();
+    return Make(picture, cropRect);
 }
 
 void SkPictureImageFilter::flatten(SkWriteBuffer& buffer) const {