Default dialog button bug

This issue can be reproduced with the dialogs/extension example.

1. Launch the example. The "Find" button is a default button for this dialog.
2. Click on the "Find" button.
3. Click in the "Find what" entry text field. The "Find" button has lost its default button behavior and the proper visual
frame
4. Repeat steps 2 and 3, in that order. The "Find" button" is now actually a default button again.