This is a quick gist for examining the list of EdgeHTML supported webkit properties that can be run on any device. This helps to narrow down why certain properties were added since not all WebKit browsers support all of the properties. This list tends to be a union of Chrome 42+ and iOS 8 Safari.

test_edgehtml_webkitprefixes.html

<div id="log" style="whitespace: pre"></div>

test_edgehtml_webkitprefixes.js

// http://jsfiddle.net/cf3mww5n/1/
function GlobalConstructorCheck(prop) {
    // TODO: Additional validation
    return prop in window; 
}
function WindowCheck(prop) {
    return prop in window;
}
function ElementCheck(prop) {
    var elem = document.body;
    return prop in elem;
}
function ComputedStyleCheck(prop) {
    var cs = window.getComputedStyle(document.body);
    return prop in cs;
}
function FullScreenChecks(prop) {
    var media = document.createElement("video");
    return (prop in media || prop in document || prop in document.body);
}

var WebKitPropertyExistenceChecks = [
    { prop: "WebKitPoint", test: GlobalConstructorCheck }, 
    { prop: "WebKitCSSMatrix", test: GlobalConstructorCheck }, 

    { prop: "webkitConvertPointFromNodeToPage", test: WindowCheck }, 
    { prop: "webkitConvertPointFromPageToNode", test: WindowCheck }, 

    { prop: "webkitMatchesSelector", test: ElementCheck }, 

    { prop: "webkitAnimation", test: ComputedStyleCheck }, 
    { prop: "webkitAnimationDelay", test: ComputedStyleCheck }, 
    { prop: "webkitAnimationDirection", test: ComputedStyleCheck }, 
    { prop: "webkitAnimationDuration", test: ComputedStyleCheck }, 
    { prop: "webkitAnimationFillMode", test: ComputedStyleCheck }, 
    { prop: "webkitAnimationIterationCount", test: ComputedStyleCheck }, 
    { prop: "webkitAnimationName", test: ComputedStyleCheck }, 
    { prop: "webkitAnimationPlayState", test: ComputedStyleCheck }, 
    { prop: "webkitAnimationTimingFunction", test: ComputedStyleCheck }, 
    { prop: "webkitBackground", test: ComputedStyleCheck }, 
    { prop: "webkitBackgroundAttachment", test: ComputedStyleCheck }, 
    { prop: "webkitBackgroundClip", test: ComputedStyleCheck }, 
    { prop: "webkitBackgroundColor", test: ComputedStyleCheck }, 
    { prop: "webkitBackgroundImage", test: ComputedStyleCheck }, 
    { prop: "webkitBackgroundOrigin", test: ComputedStyleCheck }, 
    { prop: "webkitBackgroundPosition", test: ComputedStyleCheck }, 
    { prop: "webkitBackgroundPositionX", test: ComputedStyleCheck }, 
    { prop: "webkitBackgroundPositionY", test: ComputedStyleCheck }, 
    { prop: "webkitBackgroundRepeat", test: ComputedStyleCheck }, 
    { prop: "webkitBackgroundSize", test: ComputedStyleCheck }, 
    { prop: "webkitBorderBottomLeftRadius", test: ComputedStyleCheck }, 
    { prop: "webkitBorderBottomRightRadius", test: ComputedStyleCheck }, 
    { prop: "webkitBorderImage", test: ComputedStyleCheck }, 
    { prop: "webkitBorderImageOutset", test: ComputedStyleCheck }, 
    { prop: "webkitBorderImageRepeat", test: ComputedStyleCheck }, 
    { prop: "webkitBorderImageSlice", test: ComputedStyleCheck }, 
    { prop: "webkitBorderImageSource", test: ComputedStyleCheck }, 
    { prop: "webkitBorderImageWidth", test: ComputedStyleCheck }, 
    { prop: "webkitBorderRadius", test: ComputedStyleCheck }, 
    { prop: "webkitBorderTopLeftRadius", test: ComputedStyleCheck }, 
    { prop: "webkitBorderTopRightRadius", test: ComputedStyleCheck }, 
    { prop: "webkitBoxSizing", test: ComputedStyleCheck }, 
    { prop: "webkitFilter", test: ComputedStyleCheck }, 
    { prop: "webkitAlignContent", test: ComputedStyleCheck }, 
    { prop: "webkitAlignItems", test: ComputedStyleCheck }, 
    { prop: "webkitAlignSelf", test: ComputedStyleCheck }, 
    { prop: "webkitBoxAlign", test: ComputedStyleCheck }, 
    { prop: "webkitBoxDirection", test: ComputedStyleCheck }, 
    { prop: "webkitBoxFlex", test: ComputedStyleCheck }, 
    { prop: "webkitBoxOrdinalGroup", test: ComputedStyleCheck }, 
    { prop: "webkitBoxOrient", test: ComputedStyleCheck }, 
    { prop: "webkitBoxPack", test: ComputedStyleCheck }, 
    { prop: "webkitFlex", test: ComputedStyleCheck }, 
    { prop: "webkitFlexBasis", test: ComputedStyleCheck }, 
    { prop: "webkitFlexDirection", test: ComputedStyleCheck }, 
    { prop: "webkitFlexFlow", test: ComputedStyleCheck }, 
    { prop: "webkitFlexGrow", test: ComputedStyleCheck }, 
    { prop: "webkitFlexShrink", test: ComputedStyleCheck }, 
    { prop: "webkitFlexWrap", test: ComputedStyleCheck }, 
    { prop: "webkitJustifyContent", test: ComputedStyleCheck }, 
    { prop: "webkitOrder", test: ComputedStyleCheck }, 
    { prop: "webkitAppearance", test: ComputedStyleCheck }, 
    { prop: "webkitColumnBreakAfter", test: ComputedStyleCheck }, 
    { prop: "webkitColumnBreakBefore", test: ComputedStyleCheck }, 
    { prop: "webkitColumnBreakInside", test: ComputedStyleCheck }, 
    { prop: "webkitColumnCount", test: ComputedStyleCheck }, 
    { prop: "webkitColumnGap", test: ComputedStyleCheck }, 
    { prop: "webkitColumnRule", test: ComputedStyleCheck }, 
    { prop: "webkitColumnRuleColor", test: ComputedStyleCheck }, 
    { prop: "webkitColumnRuleStyle", test: ComputedStyleCheck }, 
    { prop: "webkitColumnRuleWidth", test: ComputedStyleCheck }, 
    { prop: "webkitColumnSpan", test: ComputedStyleCheck }, 
    { prop: "webkitColumnWidth", test: ComputedStyleCheck }, 
    { prop: "webkitColumns", test: ComputedStyleCheck }, 
    { prop: "webkitTextFillColor", test: ComputedStyleCheck }, 
    { prop: "webkitBackfaceVisibility", test: ComputedStyleCheck }, 
    { prop: "webkitPerspective", test: ComputedStyleCheck }, 
    { prop: "webkitPerspectiveOrigin", test: ComputedStyleCheck }, 
    { prop: "webkitTransform", test: ComputedStyleCheck }, 
    { prop: "webkitTransformOrigin", test: ComputedStyleCheck }, 
    { prop: "webkitTransformStyle", test: ComputedStyleCheck }, 
    { prop: "webkitTransition", test: ComputedStyleCheck }, 
    { prop: "webkitTransitionDelay", test: ComputedStyleCheck }, 
    { prop: "webkitTransitionDuration", test: ComputedStyleCheck }, 
    { prop: "webkitTransitionProperty", test: ComputedStyleCheck }, 
    { prop: "webkitTransitionTimingFunction", test: ComputedStyleCheck }, 
    { prop: "webkitWritingMode", test: ComputedStyleCheck }, 
    { prop: "webkitTapHighlightColor", test: ComputedStyleCheck }, 
    { prop: "webkitTextSizeAdjust", test: ComputedStyleCheck }, 
    { prop: "webkitUserSelect", test: ComputedStyleCheck }, 

    { prop: "onwebkitfullscreenchange", test: FullScreenChecks }, 
    { prop: "onwebkitfullscreenerror", test: FullScreenChecks }, 
    { prop: "webkitCancelFullScreen", test: FullScreenChecks }, 
    { prop: "webkitCurrentFullScreenElement", test: FullScreenChecks }, 
    { prop: "webkitDisplayingFullscreen", test: FullScreenChecks }, 
    { prop: "webkitEnterFullScreen", test: FullScreenChecks }, 
    { prop: "webkitEnterFullscreen", test: FullScreenChecks }, 
    { prop: "webkitExitFullScreen", test: FullScreenChecks }, 
    { prop: "webkitExitFullscreen", test: FullScreenChecks }, 
    { prop: "webkitFullscreenElement", test: FullScreenChecks }, 
    { prop: "webkitFullscreenEnabled", test: FullScreenChecks }, 
    { prop: "webkitIsFullScreen", test: FullScreenChecks }, 
    { prop: "webkitRequestFullScreen", test: FullScreenChecks }, 
    { prop: "webkitRequestFullscreen", test: FullScreenChecks }, 
    { prop: "webkitSupportsFullscreen", test: FullScreenChecks }
];

var logger = document.getElementById("log");
WebKitPropertyExistenceChecks.forEach(function (propCheck) {
    var exists = propCheck.test(propCheck.prop);
    var logLine = document.createElement("div");
    if (exists) {
        var bold = document.createElement("b");
        bold.appendChild(document.createTextNode(propCheck.prop));
        logLine.appendChild(bold);
    }
    else {
        logLine.appendChild(document.createTextNode(propCheck.prop));
    }
    logger.appendChild(logLine);
});