change flattenable factory to return sk_sp

src/effects/SkPixelXorXfermode.cpp

Index: src/effects/SkPixelXorXfermode.cpp
diff --git a/src/effects/SkPixelXorXfermode.cpp b/src/effects/SkPixelXorXfermode.cpp
index 4ad3f1bd766a91c13679afe5d584967cd84a238e..d8861e6df111c37fef44e67719c23cc766380a69 100644
--- a/src/effects/SkPixelXorXfermode.cpp
+++ b/src/effects/SkPixelXorXfermode.cpp
@@ -26,8 +26,8 @@ void SkPixelXorXfermode::flatten(SkWriteBuffer& wb) const {
                                 SkGetPackedB32(fOpColor)));
 }
 
-SkFlattenable* SkPixelXorXfermode::CreateProc(SkReadBuffer& buffer) {
-    return Make(buffer.readColor()).release();
+sk_sp<SkFlattenable> SkPixelXorXfermode::CreateProc(SkReadBuffer& buffer) {
+    return Make(buffer.readColor());
 }
 
 #ifndef SK_IGNORE_TO_STRING