src/vs/base/browser/ui/tree/abstractTree.ts/AbstractTree/onDidChangeContentHeight
class AbstractTree:	get onDidChangeContentHeight(): Event<number> {
		let result = this.view.onDidChangeContentHeight;

		if (this.typeFilterController) {
			result = Event.any(result, Event.map(this.typeFilterController.onDidChangeEmptyState, () => this.contentHeight));
		}

		return result;
	}