Comment 12 for bug 1417118

I think I (finally) found the culprit. When the entire text in the address bar is selected (which happens programatically when giving focus to the address bar), the TextField widget displays selection handles to allow the user to resize the selection. The mouse areas to interact with them are wider than the actual handles, and the left one overlaps with the action button. I’m attaching a screenshot that demonstrates this visually (I added a semi-transparent green rectangle that outlines the mouse areas for the handles).