add iOS build benchmarks (#35749)

dev/devicelab/bin/tasks/build_benchmark.dart

@@ -8,5 +8,5 @@ import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/build_benchmarks.dart';
 
 Future<void> main() async {
-  await task(createBuildbenchmarkTask());
+  await task(createAndroidBuildBenchmarkTask());
 }

dev/devicelab/bin/tasks/build_benchmark_ios.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 'package:flutter_devicelab/framework/framework.dart';
+import 'package:flutter_devicelab/tasks/build_benchmarks.dart';
+
+Future<void> main() async {
+  await task(createIosBuildBenchmarkTask());
+}

dev/devicelab/lib/tasks/build_benchmarks.dart

@@ -10,20 +10,32 @@ import 'package:path/path.dart' as path;
 
 final Directory helloWorldDir = dir(path.join(flutterDirectory.path, 'examples', 'hello_world'));
 
-/// Creates a device lab build benchmark.
-TaskFunction createBuildbenchmarkTask() {
+/// Creates a devicelab build benchmark for Android.
+TaskFunction createAndroidBuildBenchmarkTask() {
   return () async {
+    return createBuildCommand('apk');
+  };
+}
+
+/// Creates a devicelab build benchmark for iOS.
+TaskFunction createIosBuildBenchmarkTask() {
+  return () async {
+    return createBuildCommand('ios');
+  };
+}
+
+Future<TaskResult> createBuildCommand(String buildKind) {
   return inDirectory<TaskResult>(helloWorldDir, () async {
     final Stopwatch stopwatch = Stopwatch()
       ..start();
     final Process initialBuild = await startProcess(
       path.join(flutterDirectory.path, 'bin', 'flutter'),
-        <String>['build', 'apk', '--debug'],
+      <String>['build', buildKind, '--debug'],
       environment: null,
     );
     int exitCode = await initialBuild.exitCode;
     if (exitCode != 0) {
-        return TaskResult.failure('Failed to build debug APK');
+      return TaskResult.failure('Failed to build debug app');
     }
     final int initialBuildMilliseconds = stopwatch.elapsedMilliseconds;
     stopwatch
@@ -31,34 +43,34 @@ TaskFunction createBuildbenchmarkTask() {
       ..start();
     final Process secondBuild = await startProcess(
       path.join(flutterDirectory.path, 'bin', 'flutter'),
-        <String>['build', 'apk', '--debug'],
+      <String>['build', buildKind, '--debug'],
       environment: null,
     );
     exitCode = await secondBuild.exitCode;
     if (exitCode != 0) {
-        return TaskResult.failure('Failed to build debug APK');
+      return TaskResult.failure('Failed to build debug app');
     }
     final int secondBuildMilliseconds = stopwatch.elapsedMilliseconds;
     final Process newBuildConfig = await startProcess(
       path.join(flutterDirectory.path, 'bin', 'flutter'),
-        <String>['build', 'apk', '--profile'],
+      <String>['build', buildKind, '--profile'],
       environment: null,
     );
     exitCode = await newBuildConfig.exitCode;
     if (exitCode != 0) {
-        return TaskResult.failure('Failed to build profile APK');
+      return TaskResult.failure('Failed to build profile app');
     }
     stopwatch
       ..reset()
       ..start();
     final Process thirdBuild = await startProcess(
       path.join(flutterDirectory.path, 'bin', 'flutter'),
-        <String>['build', 'apk', '--debug'],
+      <String>['build', buildKind, '--debug'],
       environment: null,
     );
     exitCode = await thirdBuild.exitCode;
     if (exitCode != 0) {
-        return TaskResult.failure('Failed to build debug APK');
+      return TaskResult.failure('Failed to build debug app');
     }
     final int thirdBuildMilliseconds = stopwatch.elapsedMilliseconds;
     stopwatch.stop();
@@ -68,5 +80,4 @@ TaskFunction createBuildbenchmarkTask() {
     allResults['after_config_change_build_debug_millis'] = thirdBuildMilliseconds.toDouble();
     return TaskResult.success(allResults, benchmarkScoreKeys: allResults.keys.toList());
   });
-  };
 }

dev/devicelab/manifest.yaml

@@ -489,6 +489,13 @@ tasks:
     required_agent_capabilities: ["mac/ios"]
     flaky: true
 
+  build_benchmark_ios:
+    description: >
+      Measures iOS build performance across config changes.
+    stage: devicelab_ios
+    required_agent_capabilities: ["mac/ios"]
+    flaky: true
+
   # Tests running on Windows host
 
   flavors_test_win: