Use polish() and updatePolish() instead of LayoutRequest

This makes the code slightly prettier, but can also remove some
flickering (if the LayoutRequest wasn't delivered until *after* the
rendering was done)

Change-Id: Id78b5c25b5f1795a74524559971410e29352ca7a
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>