Don't hide wallpaper if surface is destroyed due to drag resizing

We change surface from small to fullscreen size upon resizing,
and keep the old surface around until first draw finishes on the
new surface. This shouln't affect wallpaper. Hiding the wallpaper
causes the background to black out on every surface mode toggle.

bug: 25439788
Change-Id: I28c957dfaf1cc7f28e28cc00d8e97b8efb905349