acpi: Give WM time to draw xscreensaver window on suspend.

This is just a hacky workaround for a race where we suspend
before the screen gets updated, resulting in the previous
contents being briefly visible on resume.  xscreensaver
avoids this in non-compositing setups by syncing with the X
server, but screen updates are asynchronous when compositing
is being used.

BUG=chromium-os:2250
TEST=tried it

Review URL: http://codereview.chromium.org/1690003
1 file changed