Put action button icon on Firefox address bar

put-icon-on-firefox-address-bar.js

var loadUrlbarButton = function(doc, urlBtnClick) {
    var urlBarIcons = doc.getElementById('urlbar-icons')
    var btn = doc.createElement('toolbarbutton');
    btn.setAttribute('id', 'my-id');
    btn.setAttribute('image', require('sdk/self').data.url('my-icon.png'));
    btn.addEventListener('command', urlBtnClick, false);
    urlBarIcons.appendChild(btn);
    return btn;
}

var doc = require('sdk/window/utils').getMostRecentBrowserWindow().document;

var onBtnClick = function(event) {
    //do something when URL bar button is clicked
}

var urlbarButton = loadUrlbarButton(doc, onBtnClick);