[whatwg] Introducing new elements is expensive

[Dean Edwards]

Anne van Kesteren wrote:
> 
>   <output value="bar">foo</output>
> 
> Legacy UAs show "foo" where WF2 UAs show "bar".
> 
> 

This is not consistent with <textarea>. I think they should behave the 
same. <output> is effectively a read-only <textarea>.

-dean