Please describe the problem:
When the panel is hidden, and the user try to drag and drop some object to it, sometimes the panel won't expand.

Steps to reproduce:
1. Make sure the auto-hide option of the panel that contains the windows list is on
1. Click in one window in the windows list and drag fast outside of the panel
2. The panel will hide
3. When you try to drop the dragged item to some panel, it won't expand anymore


Actual results:
The panel won't expand.

Expected results:
The panel should expand.

Does this happen every time?
No. When you do the same thing with a launcher item, it works correctly.
And when you drag the window slowly, it also works.

Other information: