migrate hot reload benchmark to the new devicelab framework (#5878)

dev/devicelab/bin/tasks/hot_mode_dev_cycle__benchmark.dart

+// Copyright (c) 2016 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:io';
+
+import 'package:path/path.dart' as path;
+
+import 'package:flutter_devicelab/framework/adb.dart';
+import 'package:flutter_devicelab/framework/framework.dart';
+import 'package:flutter_devicelab/framework/utils.dart';
+
+void main() {
+  task(() async {
+    Adb device = await adb();
+    await device.unlock();
+    Directory appDir =
+        dir(path.join(flutterDirectory.path, 'examples/flutter_gallery'));
+    File benchmarkFile = file(path.join(appDir.path, 'hot_benchmark.json'));
+    rm(benchmarkFile);
+    await inDirectory(appDir, () async {
+      return await flutter('run',
+          options: <String>['--hot', '-d', device.deviceId, '--benchmark'],
+          canFail: false);
+    });
+    return new TaskResult.successFromFile(benchmarkFile,
+        benchmarkScoreKeys: <String>[
+          'hotReloadMillisecondsToFrame',
+          'hotRestartMillisecondsToFrame'
+        ]);
+  });
+}

dev/devicelab/manifest.yaml

@@ -103,6 +103,12 @@ tasks:
     stage: devicelab
     required_agent_capabilities: ["has-android-device"]
 
+  hot_mode_dev_cycle__benchmark:
+    description: >
+      Measures the performance of Dart VM hot patching feature.
+    stage: devicelab
+    required_agent_capabilities: ["has-android-device"]
+
 
   # iOS on-device tests