change flattenable factory to return sk_sp

tools/debugger/SkDrawCommand.cpp

Index: tools/debugger/SkDrawCommand.cpp
diff --git a/tools/debugger/SkDrawCommand.cpp b/tools/debugger/SkDrawCommand.cpp
index a32e0b6211218551d67ff7594b313e87240ae1bd..d868418d54ba8b4506fbaa05bb38a2f88f6979ec 100644
--- a/tools/debugger/SkDrawCommand.cpp
+++ b/tools/debugger/SkDrawCommand.cpp
@@ -726,12 +726,12 @@ static SkFlattenable* load_flattenable(Json::Value jsonFlattenable,
     const void* data;
     int size = decode_data(jsonFlattenable[SKDEBUGCANVAS_ATTRIBUTE_DATA], urlDataManager, &data);
     SkValidatingReadBuffer buffer(data, size);
-    SkFlattenable* result = factory(buffer);
+    sk_sp<SkFlattenable> result = factory(buffer);
     if (!buffer.isValid()) {
         SkDebugf("invalid buffer loading flattenable\n");
         return nullptr;
     }
-    return result;
+    return result.release();
 }
 
 static SkColorType colortype_from_name(const char* name) {