Visible for testing.\n */\nfunction setAbortableTimeout(\n signal: AnalyticsAbortSignal,\n throttleEndTimeMillis: number\n): Promise {\n return new Promise((resolve, reject) => {\n // Derives backoff from given end time, normalizing negative numbers to zero.\n const backoffMillis = Math.max(throttleEndTimeMillis - Date.now(), 0);\n\n const timeout = setTimeout(resolve, backoffMillis);\n\n // Adds listener, rather than sets onabort, because signal is a shared object.\n signal.addEventListener(() => {\n clearTimeout(timeout);\n // If the request completes before this timeout, the rejection has no effect.\n reject(\n ERROR_FACTORY.create(AnalyticsError.FETCH_THROTTLE, {\n throttleEndTimeMillis\n })\n );\n });\n });\n}\n\ntype RetriableError = FirebaseError & { customData: { httpStatus: string } };\n\n/**\n * Returns true if the {@link Error} indicates a fetch request may succeed later.\n */\nfunction isRetriableError(e: Error): e is RetriableError {\n if (!(e instanceof FirebaseError) || !e.customData) {\n return false;\n }\n\n // Uses string index defined by ErrorData, which FirebaseError implements.\n const httpStatus = Number(e.customData['httpStatus']);\n\n return (\n httpStatus === 429 ||\n httpStatus === 500 ||\n httpStatus === 503 ||\n httpStatus === 504\n );\n}\n\n/**\n * Shims a minimal AbortSignal (copied from Remote Config).\n *\n *