we can't shift+Tab out of the editor if there is no focusable element before the editor

[Satya Minnekanti]

To reproduce the defect:

Open Replace by Class sample.

Use Tab key to navigate in to the editor.

Now Press Shift + Tab.

Expected Result: Focus should go back to browser since there is no focusable element before the editor.

Actual Result: Focus/Cursor still remain in the editor

This is an Accessibility Issue

[Jakub Ś]

Issue has been reproducible in Firefox, Opera and Webkit from CKEditor 3.0.

Seems to be working fine in IE.