Clone hot reload benchmark for --preview-dart-2 option. (#12251)

* Clone hot reload benchmark for --preview-dart-2 option.

* Get rid of linux and win preview_dart_2 (only android would be sufficient for now). Refactor code into lib/tasks

* Revert 2016 to 2017

* Mark new test as flaky

dev/devicelab/bin/tasks/hot_mode_dev_cycle__benchmark.dart

@@ -2,34 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:io';
+import 'dart:async';
 
-import 'package:path/path.dart' as path;
-
-import 'package:flutter_devicelab/framework/adb.dart';
+import 'package:flutter_devicelab/tasks/hot_mode_tests.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
-import 'package:flutter_devicelab/framework/utils.dart';
 
-void main() {
-  task(() async {
-    final Device device = await devices.workingDevice;
-    await device.unlock();
-    final Directory appDir =
-        dir(path.join(flutterDirectory.path, 'examples/flutter_gallery'));
-    final 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', '--verbose'],
-          canFail: false);
-    });
-    return new TaskResult.successFromFile(benchmarkFile,
-        benchmarkScoreKeys: <String>[
-          'hotReloadMillisecondsToFrame',
-          'hotRestartMillisecondsToFrame',
-          'hotReloadDevFSSyncMilliseconds',
-          'hotReloadFlutterReassembleMilliseconds',
-          'hotReloadVMReloadMilliseconds',
-        ]);
-  });
+Future<Null> main() async {
+  await task(createHotModeTest());
 }

dev/devicelab/bin/tasks/hot_mode_dev_cycle__preview_dart_2_benchmark.dart

+// Copyright (c) 2017 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 'package:flutter_devicelab/tasks/hot_mode_tests.dart';
+import 'package:flutter_devicelab/framework/framework.dart';
+
+Future<Null> main() async {
+  await task(createHotModeTest(isPreviewDart2: true));
+}

dev/devicelab/bin/tasks/hot_mode_dev_cycle_linux__benchmark.dart

@@ -2,8 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'hot_mode_dev_cycle__benchmark.dart' as hot_mode_dev_cycle_benchmark;
+import 'dart:async';
 
-void main() {
-  hot_mode_dev_cycle_benchmark.main();
+import 'package:flutter_devicelab/tasks/hot_mode_tests.dart';
+import 'package:flutter_devicelab/framework/framework.dart';
+
+Future<Null> main() async {
+  await task(createHotModeTest());
 }

dev/devicelab/bin/tasks/hot_mode_dev_cycle_win__benchmark.dart

@@ -2,8 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'hot_mode_dev_cycle__benchmark.dart' as hot_mode_dev_cycle_benchmark;
+import 'dart:async';
 
-void main() {
-  hot_mode_dev_cycle_benchmark.main();
+import 'package:flutter_devicelab/tasks/hot_mode_tests.dart';
+import 'package:flutter_devicelab/framework/framework.dart';
+
+Future<Null> main() async {
+  await task(createHotModeTest());
 }

dev/devicelab/lib/tasks/hot_mode_tests.dart

+// Copyright 2017 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 '../framework/adb.dart';
+import '../framework/framework.dart';
+import '../framework/utils.dart';
+
+TaskFunction createHotModeTest({ bool isPreviewDart2: false }) {
+  return () async {
+    final Device device = await devices.workingDevice;
+    await device.unlock();
+    final Directory appDir =
+    dir(path.join(flutterDirectory.path, 'examples/flutter_gallery'));
+    final File benchmarkFile = file(path.join(appDir.path, 'hot_benchmark.json'));
+    rm(benchmarkFile);
+    final List<String> options = <String>[
+      '--hot', '-d', device.deviceId, '--benchmark', '--verbose'
+    ];
+    if (isPreviewDart2)
+      options.add('--preview-dart-2');
+    await inDirectory(appDir, () async {
+      return await flutter('run', options: options, canFail: false);
+    });
+    return new TaskResult.successFromFile(benchmarkFile,
+        benchmarkScoreKeys: <String>[
+          'hotReloadMillisecondsToFrame',
+          'hotRestartMillisecondsToFrame',
+          'hotReloadDevFSSyncMilliseconds',
+          'hotReloadFlutterReassembleMilliseconds',
+          'hotReloadVMReloadMilliseconds',
+        ]);
+  };
+}

dev/devicelab/manifest.yaml

@@ -96,6 +96,14 @@ tasks:
     stage: devicelab
     required_agent_capabilities: ["has-android-device"]
 
+  hot_mode_dev_cycle__preview_dart_2_benchmark:
+    description: >
+      Measures the performance of Dart VM hot patching feature under
+      --preview-dart-2 option, that enables Dart 2.0 frontend.
+    stage: devicelab
+    required_agent_capabilities: ["has-android-device"]
+    flaky: true
+
   complex_layout_scroll_perf__memory:
     description: >
       Measures memory usage of the scroll performance test.