70-480 Transform affecting fixed children

Apparently setting a transform creates a new Stacking Context even for "Fixed" children...

by Jeroen Heijmans

HTML

Outer test
<div id="inner">
    INNER
    <div id="fixed">
        FIXED
    </div>
</div>

<button onclick="javascript:toggleClass()">Toggle "rotate(0deg)" on inner div</button>

CSS

div {
    border: 1px solid gray;
    margin: 8px;
}

#fixed {
    position: fixed;
    top: 0;
    right: 50%;
}

.explicitZeroRotation {
    -webkit-transform: rotate(0deg);
}

JavaScript

function toggleClass() {
    var el = document.getElementById('inner');
    el.className === "explicitZeroRotation" ? el.className = "" : el.className = "explicitZeroRotation";
}