Slow flood fill with QPainter canvas

[LukasT.dev@gmail.com]

Hello,

the flood fill is still slow even we optimzed the filling algorithm.
Here is callgrind log of running krita with QPainter canvas 
http://valdyas.org/~lukast/projection-floodfill.tar.gz

It seems like projection or pyramids are slow or something. The flood fill is 
also slow for OpenGL canvas. I will do the valgrinding.

Dmitry, can you check it out?