The checker pattern drawing area is determined without taking the scaling factor into account. The pattern does not paint correctly when scaling is other than 1, except on the top of the document.
Created attachment 55974 [details]
Use the dirty rect that has been adjusted for scaling instead of the original one
Transmitting file data ..
Committed revision 59363.
Revision r59363 cherry-picked into qtwebkit-2.0 with commit 59c4c96c6aa7342f59956b6cb530f114cdfdcba5