When I apply the patch for [bug 947093](https://bugzilla.mozilla.org/show_bug.cgi?id=947093), it looks like the tabs.css `[role="tablist"] > [role="tab"] {` background-color of white may be interfering with this, makes this bottom bar white. Also, with the loss of the bottom-toolbar style, there is no black background for it any more.

So I think the style conflicts with bug 947093 should be sorted out before landing this.