function closeLightnessShades(element)
        {
            this._shadesContainer.classList.add("hidden");
            element.classList.remove("spectrum-shades-shown");
            this._shadesContainer.ownerDocument.removeEventListener("mousedown", this._shadesCloseHandler, true);
            delete this._shadesCloseHandler;
        }
@param {!Element} element
@this {!WebInspector.Spectrum}