plugins/glide: Subdivide window quad grid
The way the glide effect works is that it takes 2D geometry and applies the perspective projection to it on the CPU side. The reason we do it is that the scene is 2D.
However, this leaves us with the well known problem where a texture that's mapped to a trapezoid won't be correctly interpolated along the diagonal.
It can addressed by performing a perspective division in the fragment shader, but given the way the effect is structured, it's off the table. So instead subdivide the window grid.
(cherry picked from commit 7eb9f75a)