src/vs/workbench/contrib/webview/browser/overlayWebview.ts/OverlayWebview/container
class OverlayWebview:	public get container(): HTMLElement {
		if (this._isDisposed) {
			throw new Error(`OverlayWebview has been disposed`);
		}

		if (!this._container) {
			const node = document.createElement('div');
			node.style.position = 'absolute';
			node.style.overflow = 'hidden';
			this._container = new FastDomNode(node);
			this._container.setVisibility('hidden');

			// Webviews cannot be reparented in the dom as it will destroy their contents.
			// Mount them to a high level node to avoid this.
			this._layoutService.container.appendChild(node);
		}

		return this._container.domNode;
	}