performance decrease after upgrade to 2.5.11

[zhengzhibo]

Version

2.5.11

Reproduction link

https://jsfiddle.net/rcxucnbg/1/

Steps to reproduce

after this change 13196b2
(13196b23 fix: clone slot nodes for render fn usage as well)

render function become slow

compare
vue 2.5.2 https://jsfiddle.net/rcxucnbg
vue 2.5.11 https://jsfiddle.net/rcxucnbg/1

when child node is a component, it become even more obvious

What is expected?

render faster when scrolling

What is actually happening?

slow