Benchmark for un-triaged image results on Flutter Gold (#40634)

dev/devicelab/bin/tasks/flutter_gold_triage.dart

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:flutter_devicelab/framework/framework.dart';
+
+const String _kTriageCountKey = 'count';
+
+Future<TaskResult> getTriageCount() async {
+  final HttpClient skiaClient = HttpClient();
+  int digestCount = 0;
+  try {
+    final HttpClientRequest request = await skiaClient.getUrl(Uri.parse(
+      'https://flutter-gold.skia.org/json/trstatus'
+    ));
+    final HttpClientResponse response = await request.close();
+    final String responseBody = await response.transform(utf8.decoder).join();
+    final Map<String, dynamic> json = jsonDecode(responseBody);
+    digestCount = json['corpStatus'][0]['untriagedCount'];
+  } catch(e) {
+    return TaskResult.failure(e.toString());
+  }
+  return TaskResult.success(
+    <String, dynamic>{_kTriageCountKey: digestCount},
+    benchmarkScoreKeys: <String>[_kTriageCountKey],
+  );
+}
+
+Future<void> main() async {
+  await task(() => getTriageCount());
+}

dev/devicelab/manifest.yaml

@@ -655,6 +655,12 @@ tasks:
     stage: devicelab
     required_agent_capabilities: ["linux/android"]
 
+  flutter_gold_triage:
+    description: >
+      Checks the number of un-triaged image digests from Flutter Gold.
+    stage: devicelab
+    required_agent_capabilities: ["linux/android"]
+
   # run_without_leak_linux:
   #   description: >
   #     Checks that `flutter run` does not leak dart on Linux.