src/vs/base/browser/ui/grid/gridview.ts/GridView/root
class GridView:	private set root(root: BranchNode) {
		const oldRoot = this._root;

		if (oldRoot) {
			this.element.removeChild(oldRoot.element);
			oldRoot.dispose();
		}

		this._root = root;
		this.element.appendChild(root.element);
		this.onDidSashResetRelay.input = root.onDidSashReset;
		this._onDidChange.input = Event.map(root.onDidChange, () => undefined); // TODO
		this._onDidScroll.input = root.onDidScroll;
	}