src/vs/workbench/api/common/extHostTreeViews.ts/ExtHostTreeView/refreshNode
class ExtHostTreeView:	private refreshNode(treeItemHandle: TreeItemHandle): Promise<TreeNode | null> {
		const extElement = this.getExtensionElement(treeItemHandle);
		if (extElement) {
			const existing = this.nodes.get(extElement);
			if (existing) {
				this.clearChildren(extElement); // clear children cache
				return asPromise(() => this.dataProvider.getTreeItem(extElement))
					.then(extTreeItem => {
						if (extTreeItem) {
							const newNode = this.createTreeNode(extElement, extTreeItem, existing.parent);
							this.updateNodeCache(extElement, newNode, existing, existing.parent);
							existing.dispose();
							return newNode;
						}
						return null;
					});
			}
		}
		return Promise.resolve(null);
	}