[Aurorae] Don't delay initial blit.

Summary:
Aurorae has a timer between request update and updating the contents.
This makes some sense.

However on initial creation we want to snap the contents immediately as
otherwise we may be out by a frame between a new window being mapped and
the window decoration being rendered.

Test Plan:
Ran with Auroae
Windows opened immediately seemed to have a deco straight away

Reviewers: KWin, zzag

Reviewed By: KWin, zzag

Subscribers: zzag, romangg, kwin

Tags: KWin

Differential Revision: https://phabricator.kde.org/D23332