src/vs/workbench/api/browser/mainThreadTreeViews.ts/TreeViewDataProvider/getChildren
class TreeViewDataProvider:	getChildren(treeItem?: ITreeItem): Promise<ITreeItem[]> {
		return Promise.resolve(this._proxy.$getChildren(this.treeViewId, treeItem ? treeItem.handle : undefined)
			.then(
				children => this.postGetChildren(children),
				err => {
					this.notificationService.error(err);
					return [];
				}));
	}