A short screen capture video which shows the issue
InputMethodUndoBug.mp4 (video/mp4), 259.23 KB, created by Matthew Francis on 2014-08-07 12:00:52 UTC
(hide)
 
Creator: Matthew Francis
Created: 2014-08-07 12:00:52 UTC
Size: 259.23 KB

Attachment is not viewable in your browser because its MIME type (video/mp4) is not one that your browser is able to display.

Download the attachment.

Actions: View
Attachments on bug 82293: 104222 | 104223 | 107888