[webkit-qt] accelerated compositing

[Balazs Kelemen]

> Currently we have
>
>     1) no automated functional tests
>     2) no automated performance tests
>
> for a big feature that improves performance. We have clear evidence of it 
> improving performance with manual testing - I've seen it myself and I love it. 
>
> But what do we have in place to protect ourselves from regressions or 
>   

Please let me correct if I wrong, but I think the same is true for the
tile-backingstore feature.
The difference is that it can enabled or disabled at runtime, but we
also need functional and performace
tests for that feature.

balazs