Fix surfaces scheduler so apps can draw

The cc scheduler expects to go through at least one commit before the
output surface is ready to draw, so even though we don't commit in the
surfaces service we need to pretend we do to get the scheduler into
a drawable state. This fixes the regression from
https://codereview.chromium.org/822713002/.

TBR=abarth@chromium.org

Review URL: https://codereview.chromium.org/827163002