Firefox shows 2 focus outlines while transitioning

[Nikita Vasilyev]

flying-focus.css:17-19: outline: none doesn’t work in Firefox.

"How to remove Firefox's dotted outline on BUTTONS as well as links?" suggests to use:

::-moz-focus-inner {
  border: 0;
}

Unfortunately, in Firefox 23.0.1 it only works combined with -moz-appearance: none :(
http://jsbin.com/UZOTAri/1/edit
Bootstrap uses this but I can’t pollute host’s page style.