playbook: the view jiggles to left and right with SlideViewTransition, cover or uncover mode, with transitionControlsWithContent=true

Steps to reproduce:
1.run TransitionSampler on playbook.
2.select the first item 'slide'
3.select uncover for mode, left for direction, then select transitionControlsWithContent.
4. click PushView.
5. pay attention to the label texts in the view.

Actual Results:
they jiggle to right and left slightly during the transition.

Expected Results:
no jiggling. compare it with ADL or NexusOne.

Workaround (if any):