src/vs/base/browser/ui/splitview/paneview.ts/PaneView/constructor
class PaneView:	constructor(container: HTMLElement, options: IPaneViewOptions = {}) {
		super();

		this.dnd = options.dnd;
		this.orientation = options.orientation ?? Orientation.VERTICAL;
		this.element = append(container, $('.monaco-pane-view'));
		this.splitview = this._register(new SplitView(this.element, { orientation: this.orientation }));
		this.onDidSashReset = this.splitview.onDidSashReset;
		this.onDidSashChange = this.splitview.onDidSashChange;
		this.onDidScroll = this.splitview.onDidScroll;

		const eventDisposables = this._register(new DisposableStore());
		const onKeyDown = this._register(new DomEmitter(this.element, 'keydown'));
		const onHeaderKeyDown = Event.map(Event.filter(onKeyDown.event, e => e.target instanceof HTMLElement && e.target.classList.contains('pane-header'), eventDisposables), e => new StandardKeyboardEvent(e), eventDisposables);

		this._register(Event.filter(onHeaderKeyDown, e => e.keyCode === KeyCode.UpArrow, eventDisposables)(() => this.focusPrevious()));
		this._register(Event.filter(onHeaderKeyDown, e => e.keyCode === KeyCode.DownArrow, eventDisposables)(() => this.focusNext()));
	}