[Australis] Fix on Aurora for Edit and Zoom controls

[Francesco Lodolo [:flod]]

Hi,
just a quick heads-up: a few weeks ago we noticed an inconsistent
behavior in two widgets in Australis, namely Edit controls
(Cut-Copy-Paste) and Zoom controls.
When dragged in the main window, tooltip was displayed instead of label.
Initially this went unnoticed because English is using the same text for
both entities (label and tooltip).

More details and screenshot in the bug
https://bugzilla.mozilla.org/show_bug.cgi?id=969853

This behavior has been fixed in both central and aurora. This is just an
heads-up in case you tested Australis and changed the tooltip to fit
into the available space.

One personal suggestion: when testing Australis, go in Customize mode
and drag things around to check that everything looks good.

Francesco