Normally, a new window_surface has no damage so its draw_start_ticks
value is reset at the time of the first lock_surface.

However, if contents from the old window_surface are copied to the new
one when the window_surface for a window is updated, the new
window_surface will be initially damaged. We want to reset the
draw_start_ticks value in this case too, to avoid flushes occuring soon
after such updates, during the initial redraw of the window_surface.
Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>