IE Edge will ignore inline style set variables e.g. style="--my-color: #ccc" will not overwrite any default value for my-color.

BaseElement.html

<link rel="import" href="../../../../bower_components/polymer/polymer.html">

<script>

	class BaseElement extends Polymer.Element {

		vhToPx(vh) {
			if (vh.indexOf('vh') > 0) {
				return document.documentElement.clientHeight * (parseInt(vh)/100) + '';
			}
			return vh;
		}

		ready() {
			super.ready();
			this.updateStyles({});
		}

		updateStyles(styles) {
			if (styles === undefined) {
				return;
			}
			let newStyle = styles;
			let currentStyleString = this.getAttribute('style');
			if (currentStyleString !== undefined && currentStyleString !== null && currentStyleString !== '') {
				newStyle = {};
				let currentStylesPairs = currentStyleString.split(';');
				for (let currentStylePairKey in currentStylesPairs) {
					if (currentStylesPairs.hasOwnProperty(currentStylePairKey)) {
						let currentStylePairString = currentStylesPairs[currentStylePairKey];
						if (currentStylePairString !== '') {
							let currentStylePair = currentStylePairString.split(':');
							if (currentStylePair.length === 2) {
								newStyle[currentStylePair[0]] = currentStylePair[1];
							}
						}
					}
				}

				for (var newStylePairKey in styles) {
					if (styles.hasOwnProperty(newStylePairKey)) {
						newStyle[newStylePairKey] = styles[newStylePairKey];
					}
				}
			}

			if (window.ShadyCSS && window.ShadyCSS.nativeCss === false) {
				super.updateStyles(newStyle);
			} else {
				var newStyleString = '';
				for (var key in newStyle) {
					if (newStyle.hasOwnProperty(key)) {
						newStyleString += key + ': ' + newStyle[key] + ';';
					}
				}
				this.style = newStyleString;
			}
		}

	}

</script>