Curtain move to lower right automatically from middle position.

Steps:
1. Create a project. (Qt Quick Project>Qt Quick Application. others are default)
2. Go to 'Design' view, select text and change font size to 14.
3. Go to 'Edit' view and back to 'Design' view.
3. Check the position of curtain.

Actual result:
Curtain move to lower right from middle position.
(Please see the attachment pictures.)

Expect result:
Curtain should stay in the middle position.

Comment:
Easy to reproduced but not 100%.
SDKTest Round15
Qt Creator 2.2.81(pre-2.3.0-bata)