restore = () =>
					strategy.restore(identifier, etag).then(cacheEntry => {
						if (cacheEntry === undefined) {
							gotHandlers.push((result, callback) => {
								if (result !== undefined) {
									pendingIdleTasks.set(identifier, () =>
										strategy.store(identifier, etag, result)
									);
								}
								callback();
							});
						} else {
							return cacheEntry;
						}
					})
@type {Map<string | typeof BUILD_DEPENDENCIES_KEY, () => Promise<void>>}