Migrate devicelab tasks i-z to null safety. (#85998)

dev/devicelab/bin/tasks/ios_app_with_extensions_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:convert';
 import 'dart:io';
 
@@ -18,8 +16,8 @@ Future<void> main() async {
   await task(() async {
     section('Copy test Flutter App with watchOS Companion');
 
-    String watchDeviceID;
-    String phoneDeviceID;
+    String? watchDeviceID;
+    String? phoneDeviceID;
     final Directory tempDir = Directory.systemTemp
         .createTempSync('flutter_ios_app_with_extensions_test.');
     final Directory projectDir =
@@ -127,8 +125,8 @@ Future<void> main() async {
       //    iOS 13.4 (13.4 - 17E255) - com.apple.CoreSimulator.SimRuntime.iOS-13-4
       //    tvOS 13.4 (13.4 - 17L255) - com.apple.CoreSimulator.SimRuntime.tvOS-13-4
       //    watchOS 6.2 (6.2 - 17T256) - com.apple.CoreSimulator.SimRuntime.watchOS-6-2
-      String iOSSimRuntime;
-      String watchSimRuntime;
+      String? iOSSimRuntime;
+      String? watchSimRuntime;
 
       final RegExp iOSRuntimePattern = RegExp(r'iOS .*\) - (.*)');
       final RegExp watchOSRuntimePattern = RegExp(r'watchOS .*\) - (.*)');
@@ -136,14 +134,14 @@ Future<void> main() async {
       for (final String runtime in LineSplitter.split(availableRuntimes)) {
         // These seem to be in order, so allow matching multiple lines so it grabs
         // the last (hopefully latest) one.
-        final RegExpMatch iOSRuntimeMatch = iOSRuntimePattern.firstMatch(runtime);
+        final RegExpMatch? iOSRuntimeMatch = iOSRuntimePattern.firstMatch(runtime);
         if (iOSRuntimeMatch != null) {
-          iOSSimRuntime = iOSRuntimeMatch.group(1).trim();
+          iOSSimRuntime = iOSRuntimeMatch.group(1)!.trim();
           continue;
         }
-        final RegExpMatch watchOSRuntimeMatch = watchOSRuntimePattern.firstMatch(runtime);
+        final RegExpMatch? watchOSRuntimeMatch = watchOSRuntimePattern.firstMatch(runtime);
         if (watchOSRuntimeMatch != null) {
-          watchSimRuntime = watchOSRuntimeMatch.group(1).trim();
+          watchSimRuntime = watchOSRuntimeMatch.group(1)!.trim();
         }
       }
       if (iOSSimRuntime == null || watchSimRuntime == null) {

dev/devicelab/bin/tasks/ios_content_validation_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:io';
 
 import 'package:flutter_devicelab/framework/apk_utils.dart';
@@ -46,7 +44,7 @@ Future<void> main() async {
         final Directory appBundle = applications
             .listSync()
             .whereType<Directory>()
-            .singleWhere((Directory directory) => path.extension(directory.path) == '.app', orElse: () => null);
+            .singleWhere((Directory directory) => path.extension(directory.path) == '.app');
 
         final String flutterFramework = path.join(
           appBundle.path,

dev/devicelab/bin/tasks/ios_defines_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/integration_tests.dart';

dev/devicelab/bin/tasks/ios_platform_view_tests.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/integration_tests.dart';

dev/devicelab/bin/tasks/large_image_changer_perf_android.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/framework/utils.dart';

dev/devicelab/bin/tasks/large_image_changer_perf_ios.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/framework/utils.dart';

dev/devicelab/bin/tasks/linux_chrome_dev_mode.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/web_dev_mode_tests.dart';
 

dev/devicelab/bin/tasks/macos_chrome_dev_mode.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/web_dev_mode_tests.dart';
 

dev/devicelab/bin/tasks/microbenchmarks.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/microbenchmarks.dart';

dev/devicelab/bin/tasks/microbenchmarks_ios.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/microbenchmarks.dart';

dev/devicelab/bin/tasks/module_custom_host_app_name_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:io';
 
 import 'package:flutter_devicelab/framework/apk_utils.dart';
@@ -24,7 +22,7 @@ Future<void> main() async {
 
     section('Find Java');
 
-    final String javaHome = await findJavaHome();
+    final String? javaHome = await findJavaHome();
     if (javaHome == null)
       return TaskResult.failure('Could not find Java');
     print('\nUsing JAVA_HOME=$javaHome');

dev/devicelab/bin/tasks/module_host_with_custom_build_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:io';
 
 import 'package:flutter_devicelab/framework/apk_utils.dart';
@@ -22,7 +20,7 @@ Future<void> main() async {
 
     section('Find Java');
 
-    final String javaHome = await findJavaHome();
+    final String? javaHome = await findJavaHome();
     if (javaHome == null) {
       return TaskResult.failure('Could not find Java');
     }

dev/devicelab/bin/tasks/module_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:convert';
 import 'dart:io';
 import 'dart:typed_data';
@@ -27,7 +25,7 @@ Future<void> main() async {
 
     section('Find Java');
 
-    final String javaHome = await findJavaHome();
+    final String? javaHome = await findJavaHome();
     if (javaHome == null)
       return TaskResult.failure('Could not find Java');
     print('\nUsing JAVA_HOME=$javaHome');
@@ -325,9 +323,9 @@ Future<void> main() async {
         final File apkFile = File(releaseHostApk);
         final Archive apk = ZipDecoder().decodeBytes(apkFile.readAsBytesSync());
         // Shouldn't be missing since we already checked it exists above.
-        final ArchiveFile noticesFile = apk.findFile('assets/flutter_assets/NOTICES.Z');
+        final ArchiveFile? noticesFile = apk.findFile('assets/flutter_assets/NOTICES.Z');
 
-        final Uint8List licenseData = noticesFile.content as Uint8List;
+        final Uint8List licenseData = noticesFile?.content as Uint8List;
         if (licenseData == null) {
           return TaskResult.failure('Invalid license file.');
         }

dev/devicelab/bin/tasks/module_test_ios.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:convert';
 import 'dart:io';
 import 'dart:typed_data';
@@ -20,7 +18,7 @@ import 'package:path/path.dart' as path;
 /// adding Flutter to an existing iOS app.
 Future<void> main() async {
   await task(() async {
-    String simulatorDeviceId;
+    late String simulatorDeviceId;
     section('Create Flutter module project');
 
     final Directory tempDir = Directory.systemTemp.createTempSync('flutter_module_test.');
@@ -360,7 +358,7 @@ Future<void> main() async {
         );
 
         if (testResultExit != 0) {
-          final Directory dumpDirectory = hostAgent.dumpDirectory;
+          final Directory? dumpDirectory = hostAgent.dumpDirectory;
           if (dumpDirectory != null) {
             // Zip the test results to the artifacts directory for upload.
             await inDirectory(resultBundleTemp, () {

dev/devicelab/bin/tasks/multi_widget_construction_perf__e2e_summary.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/native_ui_tests_ios32.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:io';
 
 import 'package:flutter_devicelab/framework/devices.dart';
@@ -43,8 +41,8 @@ Future<void> main() async {
     final Map<String, String> environment = Platform.environment;
     // If not running on CI, inject the Flutter team code signing properties.
     final String developmentTeam = environment['FLUTTER_XCODE_DEVELOPMENT_TEAM'] ?? 'S8QB4VV633';
-    final String codeSignStyle = environment['FLUTTER_XCODE_CODE_SIGN_STYLE'];
-    final String provisioningProfile = environment['FLUTTER_XCODE_PROVISIONING_PROFILE_SPECIFIER'];
+    final String? codeSignStyle = environment['FLUTTER_XCODE_CODE_SIGN_STYLE'];
+    final String? provisioningProfile = environment['FLUTTER_XCODE_PROVISIONING_PROFILE_SPECIFIER'];
 
     final String resultBundleTemp = Directory.systemTemp.createTempSync('flutter_native_ui_tests_ios32_xcresult.').path;
     final String resultBundlePath = path.join(resultBundleTemp, 'result');
@@ -74,7 +72,7 @@ Future<void> main() async {
     );
 
     if (testResultExit != 0) {
-      final Directory dumpDirectory = hostAgent.dumpDirectory;
+      final Directory? dumpDirectory = hostAgent.dumpDirectory;
       if (dumpDirectory != null) {
         // Zip the test results to the artifacts directory for upload.
         final String zipPath = path.join(dumpDirectory.path,

dev/devicelab/bin/tasks/new_gallery__crane_perf.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:io';
 
 import 'package:flutter_devicelab/framework/devices.dart';

dev/devicelab/bin/tasks/new_gallery__transition_perf.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:io';
 
 import 'package:flutter_devicelab/framework/devices.dart';

dev/devicelab/bin/tasks/new_gallery_ios__transition_perf.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:io';
 
 import 'package:flutter_devicelab/framework/devices.dart';

dev/devicelab/bin/tasks/picture_cache_perf__e2e_summary.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/picture_cache_perf__timeline_summary.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/platform_channel_sample_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/integration_tests.dart';

dev/devicelab/bin/tasks/platform_channel_sample_test_ios.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/integration_tests.dart';

dev/devicelab/bin/tasks/platform_channel_sample_test_swift.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/integration_tests.dart';

dev/devicelab/bin/tasks/platform_channels_benchmarks.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart' show DeviceOperatingSystem;
 import 'package:flutter_devicelab/framework/framework.dart' show task;
 import 'package:flutter_devicelab/tasks/platform_channels_benchmarks.dart' as platform_channels_benchmarks;

dev/devicelab/bin/tasks/platform_channels_benchmarks_ios.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart' show DeviceOperatingSystem;
 import 'package:flutter_devicelab/framework/framework.dart' show task;
 import 'package:flutter_devicelab/tasks/platform_channels_benchmarks.dart' as platform_channels_benchmarks;

dev/devicelab/bin/tasks/platform_interaction_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/integration_tests.dart';

dev/devicelab/bin/tasks/platform_interaction_test_ios.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/integration_tests.dart';

dev/devicelab/bin/tasks/platform_view__start_up.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/platform_view_ios__start_up.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:io';
 
 import 'package:flutter_devicelab/framework/devices.dart';

dev/devicelab/bin/tasks/platform_views_scroll_perf__timeline_summary.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/platform_views_scroll_perf_ios__timeline_summary.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/plugin_dependencies_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:convert';
 import 'dart:io';
 
@@ -24,7 +22,7 @@ Future<void> main() async {
 
     section('Find Java');
 
-    final String javaHome = await findJavaHome();
+    final String? javaHome = await findJavaHome();
     if (javaHome == null) {
       return TaskResult.failure('Could not find Java');
     }

dev/devicelab/bin/tasks/plugin_lint_mac.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:io';
 
 import 'package:flutter_devicelab/framework/framework.dart';

dev/devicelab/bin/tasks/plugin_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/plugin_tests.dart';
 

dev/devicelab/bin/tasks/plugin_test_ios.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/plugin_tests.dart';
 

dev/devicelab/bin/tasks/plugin_test_win.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/plugin_tests.dart';
 

dev/devicelab/bin/tasks/post_backdrop_filter_perf_ios__timeline_summary.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/routing_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
@@ -17,7 +15,7 @@ import 'package:path/path.dart' as path;
 
 void main() {
   task(() async {
-    int vmServicePort;
+    int? vmServicePort;
 
     final Device device = await devices.workingDevice;
     await device.unlock();
@@ -40,7 +38,7 @@ void main() {
     section('TEST WHETHER `flutter run --route` WORKS');
     await inDirectory(appDir, () async {
       final Completer<void> ready = Completer<void>();
-      bool ok;
+      late bool ok;
       print('run: starting...');
       final Process run = await startProcess(
         path.join(flutterDirectory.path, 'bin', 'flutter'),
@@ -58,7 +56,7 @@ void main() {
               print('service protocol connection available at port $vmServicePort');
               print('run: ready!');
               ready.complete();
-              ok ??= true;
+              ok = true;
             }
           }
         });

dev/devicelab/bin/tasks/run_release_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
@@ -52,7 +50,7 @@ void main() {
         <String>['--suppress-analytics', 'run', '--release', '-d', device.deviceId, 'lib/main.dart'],
         isBot: false, // we just want to test the output, not have any debugging info
       );
-      int runExitCode;
+      int? runExitCode;
       run.stdout
         .transform<String>(utf8.decoder)
         .transform<String>(const LineSplitter())

dev/devicelab/bin/tasks/service_extensions_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
@@ -19,14 +17,14 @@ import 'package:vm_service/vm_service_io.dart';
 
 void main() {
   task(() async {
-    int vmServicePort;
+    int? vmServicePort;
 
     final Device device = await devices.workingDevice;
     await device.unlock();
     final Directory appDir = dir(path.join(flutterDirectory.path, 'dev/integration_tests/ui'));
     await inDirectory(appDir, () async {
       final Completer<void> ready = Completer<void>();
-      bool ok;
+      late bool ok;
       print('run: starting...');
       final Process run = await startProcess(
         path.join(flutterDirectory.path, 'bin', 'flutter'),
@@ -43,7 +41,7 @@ void main() {
             print('service protocol connection available at port $vmServicePort');
             print('run: ready!');
             ready.complete();
-            ok ??= true;
+            ok = true;
           }
         }
       });
@@ -60,7 +58,7 @@ void main() {
 
       final VmService client = await vmServiceConnectUri('ws://localhost:$vmServicePort/ws');
       final VM vm = await client.getVM();
-      final IsolateRef isolate = vm.isolates.first;
+      final IsolateRef isolate = vm.isolates!.first;
 
       final StreamController<Event> frameEventsController = StreamController<Event>();
       final StreamController<Event> navigationEventsController = StreamController<Event>();
@@ -90,17 +88,17 @@ void main() {
 
       // validate the fields
       // {number: 8, startTime: 0, elapsed: 1437, build: 600, raster: 800}
-      print(event.extensionData.data);
-      expect(event.extensionData.data['number'] is int);
-      expect((event.extensionData.data['number'] as int) >= 0);
-      expect(event.extensionData.data['startTime'] is int);
-      expect((event.extensionData.data['startTime'] as int) >= 0);
-      expect(event.extensionData.data['elapsed'] is int);
-      expect((event.extensionData.data['elapsed'] as int) >= 0);
-      expect(event.extensionData.data['build'] is int);
-      expect((event.extensionData.data['build'] as int) >= 0);
-      expect(event.extensionData.data['raster'] is int);
-      expect((event.extensionData.data['raster'] as int) >= 0);
+      print(event.extensionData!.data);
+      expect(event.extensionData!.data['number'] is int);
+      expect((event.extensionData!.data['number'] as int) >= 0);
+      expect(event.extensionData!.data['startTime'] is int);
+      expect((event.extensionData!.data['startTime'] as int) >= 0);
+      expect(event.extensionData!.data['elapsed'] is int);
+      expect((event.extensionData!.data['elapsed'] as int) >= 0);
+      expect(event.extensionData!.data['build'] is int);
+      expect((event.extensionData!.data['build'] as int) >= 0);
+      expect(event.extensionData!.data['raster'] is int);
+      expect((event.extensionData!.data['raster'] as int) >= 0);
 
       final Future<Event> navigationFuture = navigationEvents.first;
       // This tap triggers a navigation event.
@@ -108,8 +106,8 @@ void main() {
 
       final Event navigationEvent = await navigationFuture;
       // validate the fields
-      expect(navigationEvent.extensionData.data['route'] is Map<dynamic, dynamic>);
-      final Map<dynamic, dynamic> route = navigationEvent.extensionData.data['route'] as Map<dynamic, dynamic>;
+      expect(navigationEvent.extensionData!.data['route'] is Map<dynamic, dynamic>);
+      final Map<dynamic, dynamic> route = navigationEvent.extensionData!.data['route'] as Map<dynamic, dynamic>;
       expect(route['description'] is String);
       expect(route['settings'] is Map<dynamic, dynamic>);
       final Map<dynamic, dynamic> settings = route['settings'] as Map<dynamic, dynamic>;

dev/devicelab/bin/tasks/simple_animation_perf_ios.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/smoke_catalina_hot_mode_dev_cycle_ios__benchmark.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/hot_mode_tests.dart';

dev/devicelab/bin/tasks/smoke_catalina_start_up.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';
 

dev/devicelab/bin/tasks/smoke_test_build_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/framework/task_result.dart';

dev/devicelab/bin/tasks/smoke_test_device.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/framework/task_result.dart';

dev/devicelab/bin/tasks/smoke_test_failure.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/framework/task_result.dart';
 

dev/devicelab/bin/tasks/smoke_test_success.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/framework/task_result.dart';
 

dev/devicelab/bin/tasks/smoke_test_throws.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 
 /// Smoke test of a task that fails with an exception.

dev/devicelab/bin/tasks/technical_debt__cost.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:convert';
 import 'dart:io';
 
@@ -71,23 +69,23 @@ Future<double> findCostsForFile(File file) async {
 }
 
 bool isOptingOutOfNullSafety(String line) {
-  final RegExpMatch match = dartVersionPattern.firstMatch(line);
+  final RegExpMatch? match = dartVersionPattern.firstMatch(line);
   if (match == null) {
     return false;
   }
   assert(match.groupCount == 2);
-  return Version(int.parse(match.group(1)), int.parse(match.group(2)), 0) < firstNullSafeDartVersion;
+  return Version(int.parse(match.group(1)!), int.parse(match.group(2)!), 0) < firstNullSafeDartVersion;
 }
 
 bool packageIsNullSafe(File file) {
   assert(path.basename(file.path) == 'pubspec.yaml');
   final Pubspec pubspec = Pubspec.parse(file.readAsStringSync());
-  final VersionConstraint constraint = pubspec.environment == null ? null : pubspec.environment['sdk'];
+  final VersionConstraint? constraint = pubspec.environment == null ? null : pubspec.environment!['sdk'];
   final bool hasConstraint = constraint != null && !constraint.isAny && !constraint.isEmpty;
   return hasConstraint &&
       constraint is VersionRange &&
       constraint.min != null &&
-      Version(constraint.min.major, constraint.min.minor, 0) >= firstNullSafeDartVersion;
+      Version(constraint.min!.major, constraint.min!.minor, 0) >= firstNullSafeDartVersion;
 }
 
 Future<int> findGlobalsForFile(File file) async {

dev/devicelab/bin/tasks/textfield_perf.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/textfield_perf__e2e_summary.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:async';
 
 import 'package:flutter_devicelab/framework/devices.dart';

dev/devicelab/bin/tasks/textfield_perf__timeline_summary.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/tiles_scroll_perf__timeline_summary.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/tiles_scroll_perf_ios__timeline_summary.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/tiles_scroll_perf_iphonexs__timeline_summary.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';

dev/devicelab/bin/tasks/web_benchmarks_canvaskit.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/web_benchmarks.dart';
 

dev/devicelab/bin/tasks/web_benchmarks_html.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/web_benchmarks.dart';
 

dev/devicelab/bin/tasks/web_incremental_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/web_dev_mode_tests.dart';
 

dev/devicelab/bin/tasks/web_size__compile_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/perf_tests.dart';
 

dev/devicelab/bin/tasks/windows_chrome_dev_mode.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/tasks/web_dev_mode_tests.dart';