src/vs/workbench/api/browser/viewsExtensionPoint.ts/ViewsExtensionHandler/getViewType
class ViewsExtensionHandler:	private getViewType(type: string | undefined): ViewType | undefined {
		if (type === ViewType.Webview) {
			return ViewType.Webview;
		}
		if (!type || type === ViewType.Tree) {
			return ViewType.Tree;
		}
		return undefined;
	}