Ziggurat for Firefox

gistfile1.js

var win = gBrowser.selectedBrowser.contentWindow;
var doc = win.document;
var output = doc.createElement("div");
output.id = "output";
doc.body.appendChild(output);

var style = doc.createElement("style");
style.innerHTML = "div#output { margin-top: 10em; white-space: pre; } div#output span {  padding: 0.6em; margin: 0 0.6em; border: 1px solid rgba(0, 0, 0, 0.8); border-radius: 0.2em; box-shadow: 1px 1px 1px rgba(0, 0, 0, 0.4); position: relative; bottom: 1em; background-color: #ff5454; } div#output span > span { background-color: #ffa054; } div#output span > span > span { background-color: #ffff54; } div#output span > span > span > span { background-color: #8cd446; } div#output span > span > span > span > span { background-color: #45d2b0; } div#output span > span > span > span > span > span { background-color: #438ccb; } div#output span > span > span > span > span > span > span { background-color: #8c3fc0; } div#output span > span > span > span > span > span > span > span { background-color: #d145c1; } div#output span > span > span > span > span > span > span > span > span { background-color: #ff5454; } div#output span > span > span > span > span > span > span > span > span > span { background-color: #ffa054; }";
doc.head.appendChild(style);

var dbg = new Debugger(win);
dbg.onEnterFrame = function (frame) {
    var s = doc.createElement("span");
    s.appendChild(doc.createTextNode(
        frame.callee.name + "(" + frame.arguments.join(", ") + ")"));
    output.appendChild(s);
    output = s;
    frame.onPop = function (result) {
        s.appendChild(doc.createTextNode(
            " → " + result.return));
        output = s.parentNode;
    };
};

//dbg.enabled = false;