src/vs/workbench/api/common/extHostTreeViews.ts/ExtHostTreeView/refreshHandles
class ExtHostTreeView:	private refreshHandles(itemHandles: TreeItemHandle[]): Promise<void> {
		const itemsToRefresh: { [treeItemHandle: string]: ITreeItem } = {};
		return Promise.all(itemHandles.map(treeItemHandle =>
			this.refreshNode(treeItemHandle)
				.then(node => {
					if (node) {
						itemsToRefresh[treeItemHandle] = node.item;
					}
				})))
			.then(() => Object.keys(itemsToRefresh).length ? this.proxy.$refresh(this.viewId, itemsToRefresh) : undefined);
	}