Adding a Toolbar Button in a Bootstrapped Firefox Extension

gistfile1.js

function addButton(toolbarId, buttonId, label, iconPath, firstRun) {
  var toolbar = document.getElementById(toolbarId);
  var toolbarButton = document.createElement("toolbarbutton");
  toolbarButton.setAttribute("id", buttonId);
  toolbarButton.setAttribute("type", "button");
  toolbarButton.setAttribute("removable", "true");
  toolbarButton.setAttribute("class",
    "toolbarbutton-1 chromeclass-toolbar-additional");
  toolbarButton.setAttribute("label", label);
  toolbarButton.style.listStyleImage = "url(" + iconPath + ")";

  var palette = document.getElementById("navigator-toolbox").palette;
  palette.appendChild(toolbarButton);
  var currentset = toolbar.getAttribute("currentset").split(",");
  var index = currentset.indexOf(buttonId);
  if (index == -1) {
    if (firstRun) {
      // No button yet so add it to the toolbar.
      toolbar.appendChild(toolbarButton);
      toolbar.setAttribute("currentset", toolbar.currentSet);
      document.persist(toolbar.id, "currentset");
    }
  }
  else {
    // The ID is in the currentset, so find the position and
    // insert the button there.
    var before = null;
    for (var i=index+1; i<currentset.length; i++) {
      before = document.getElementById(currentset[i]);
      if (before) {
        toolbar.insertItem(buttonId, before);
        break;
      }
    }
    if (!before) {
      toolbar.insertItem(buttonId);
    }
  }
}