Quoting a blog from 2009, "this class is responsible for figuring out which parts
of the window surface needs to be updated prior to showing it to screen, so it's
really a repaint manager."
https://blog.qt.io/blog/2009/12/16/qt-graphics-and-performance-an-overview/
What better time to do the rename than 10 years later!
Change-Id: Ibf3c3bc8c7df64ac03d72e1f71d296b62d832fee
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
6d9d4e6817