src/vs/editor/contrib/colorPicker/browser/colorPickerWidget.ts/OpacityStrip/constructor
class OpacityStrip:	constructor(container: HTMLElement, model: ColorPickerModel) {
		super(container, model);
		this.domNode.classList.add('opacity-strip');

		this._register(model.onDidChangeColor(this.onDidChangeColor, this));
		this.onDidChangeColor(this.model.color);
	}