How to use the @theia/mini-browser/lib/browser/mini-browser-content-style.MiniBrowserContentStyle.TRANSPARENT_OVERLAY function in @theia/mini-browser

protected init(): void {
        this.node.tabIndex = 0;
        this.id = WebviewWidget.FACTORY_ID + ':' + this.identifier.id;
        this.title.closable = true;
        this.addClass(WebviewWidget.Styles.WEBVIEW);

        this.toDispose.push(this.onMessageEmitter);

        this.transparentOverlay = document.createElement('div');
        this.transparentOverlay.classList.add(MiniBrowserContentStyle.TRANSPARENT_OVERLAY);
        this.transparentOverlay.style.display = 'none';
        this.node.appendChild(this.transparentOverlay);

        this.toDispose.push(this.mouseTracker.onMousedown(() => {
            if (this.element.style.display !== 'none') {
                this.transparentOverlay.style.display = 'block';
            }
        }));
        this.toDispose.push(this.mouseTracker.onMouseup(() => {
            if (this.element.style.display !== 'none') {
                this.transparentOverlay.style.display = 'none';
            }
        }));

        const element = document.createElement('iframe');
        element.className = 'webview';