src/vs/workbench/contrib/webviewView/browser/webviewViewPane.ts/WebviewViewPane/findRootContainer
class WebviewViewPane:	private findRootContainer(container: HTMLElement): HTMLElement | undefined {
		for (let el: Node | null = container; el; el = el.parentNode) {
			if (el instanceof HTMLElement) {
				if (el.classList.contains('monaco-scrollable-element')) {
					return el;
				}
			}
		}
		return undefined;
	}