Fix random error in DelegateToWidget test

Because of performance fixes to the handling of @DelegateToWidget
handling, the order in which property changes are delegated are no
longer deterministic. This patch fixes a bug in the test which caused
the update to value4 to be ignored if that was the last property to get
delegated.

Change-Id: Ie13a125b0d719894391b8ae3c9d2d899b163ebb4