add disposable listener

src/vs/base/browser/ui/list/listView.ts

@@ -469,7 +469,7 @@ export class ListView<T> implements IListView<T> {
 	}
 
 	private _setupFocusObserver(container: HTMLElement): void {
-		container.addEventListener('focus', () => {
+		addDisposableListener(container, 'focus', () => {
 			const element = getActiveElement() as HTMLElement | null;
 			if (this.activeElement !== element && element !== null) {
 				this.activeElement = element;
@@ -480,7 +480,7 @@ export class ListView<T> implements IListView<T> {
 
 	private _scrollToActiveElement(element: HTMLElement, container: HTMLElement) {
 		// The scroll event on the list only fires when scrolling down.
-		// If the active element is above the viewport, we need to scroll up. 
+		// If the active element is above the viewport, we need to scroll up.
 		const containerRect = container.getBoundingClientRect();
 		const elementRect = element.getBoundingClientRect();