Firefox to probably receive Firefox branded back button

Months ago, Mozilla introduced several visual changes in Firefox, among which a new back button, displayed with a bigger icon as compared to the forward icon, buttons that have been assimilated by users as powerful Firefox branding elements, meaning, one can easily identify a web-browser as Firefox if observes the mentioned icons or/and can name "Firefox-like buttons" on themes with similar design.

Although applied in various Firefox flavors (in other operating systems), Ubuntu version lacks this fancy element, displaying the back and forward buttons in identical shapes and sizes.

According to Mozilla's Paul Rouget, the above mentioned approach is to probably change in the future: "Today, I am trying to implement the Firefox "keyhole" back button on Linux", as seen in the bellow mockups.