content/browser/debugger/manual_tests/dom-mutation.html

<script>
function test1() {
    document.getElementById("test").src = "resources/mutate-frame.html";
}

function test2() {
    document.getElementById("test").src = "resources/mutate-frame-2.html";
}

var count = 1;
function run() {
    var container = document.getElementById("test2");
    var div = document.createElement("div");
    div.textContent = "Testing " + (count++);
    container.appendChild(div);
    if (count > 10)
        container.removeChild(container.firstChild);
}

setInterval(run, 1000);
</script>
<p>To begin test, open DevTools, Elements Panel and watch the DOM change to match the page.
Clicking the buttons will navigate the subframe, and the all the subframe child nodes should change.
Expand DOM nodes in the Elements Panel to see new nodes appearing in the list live.</p>
<div style="clear: both">
<button onclick="test1()">Test Frame 1</button>
<button onclick="test2()">Test Frame 2</button>
</div>
<div style="float: left">
<iframe id="test" src="resources/mutate-frame.html" width="200" height="300"></iframe>
</div>
<div style="float: left; margin-left: 10px;" id="test2"></div>