Number of unread items isn't displayed on latest Firefox 25.0a1

[Infocatcher]

Something changed in XBL handling, so items inside <toolbarbutton> isn't displayed (but exists in DOM).

Strange workaround:

    get statusCounter() {
        let statusCounter = document.getElementById('brief-status-counter');
        if (!statusCounter)
            return null;
        let tb = this.toolbarbutton;
        if (tb) { // Workarond for Firefox 25.0a1
            let innerBox = document.getElementById('brief-button-inner-box');
            if (innerBox && innerBox.boxObject.width == 0)
                tb.appendChild(statusCounter);
        }
        delete this.statusCounter;
        return this.statusCounter = statusCounter;
    },

[Infocatcher]

Very similar bug: https://bugzilla.mozilla.org/show_bug.cgi?id=888787#c7