[css-ui] transformed outline interoperability

Today during the conf call, we spoke about the interoperability of the  
outline property.

I've put together a very simple file illustrating an interop problem with  
regards to transformed elements.

http://florian.rivoal.net/csswg/outline.html

Gecko and webkit transform the outline, while presto draws an straight  
outline around the transformed element. (I don't know what IE does, as I  
run linux).

I think the problem with firefox's and webkit's approach is when you start  
to have 3d transforms. I don't think transforming the outline in 3d is a  
good idea. It works ok when people use it as a second border, but not when  
it is supposed to related to focusing.

  - Florian