src/vs/workbench/contrib/webview/browser/overlayWebview.ts/OverlayWebview/layoutWebviewOverElement
class OverlayWebview:	public layoutWebviewOverElement(element: HTMLElement, dimension?: Dimension) {
		if (!this._container || !this._container.parentElement) {
			return;
		}

		const frameRect = element.getBoundingClientRect();
		const containerRect = this._container.parentElement.getBoundingClientRect();
		const parentBorderTop = (containerRect.height - this._container.parentElement.clientHeight) / 2.0;
		const parentBorderLeft = (containerRect.width - this._container.parentElement.clientWidth) / 2.0;
		this._container.style.position = 'absolute';
		this._container.style.overflow = 'hidden';
		this._container.style.top = `${frameRect.top - containerRect.top - parentBorderTop}px`;
		this._container.style.left = `${frameRect.left - containerRect.left - parentBorderLeft}px`;
		this._container.style.width = `${dimension ? dimension.width : frameRect.width}px`;
		this._container.style.height = `${dimension ? dimension.height : frameRect.height}px`;
	}