Fix geometry updates in the view controller.

Move the common, and QtQuick specific code, into the view controller
to make the behavior more consistent across all platforms.

Change-Id: I89cc383fb92ee6755e8fba9baf48e3e756d04cca
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>