Ensure ScreenTransformation matrix is reset after rendering cube

Cube effect modifies the ScreenTransformation matrix. While each
window resets the matrix on a global level it's not reset. That
means if the last rendered window had the screen rotated the
ScreenTransformation keeps the rotation even after the cube
ended. This causes a rotated window in e.g. TaskbarThumbnails.

Cherry-picked from 9417a761

BUG: 299869
FIXED-IN: 4.8.4
REVIEW: 104918