Add --local-web-sdk in devicelab runner to make --ab testing work for web (#123825)

This allows us to check for performance differences in local Web SDKs.

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we expect every widget to implement].
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- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] All existing and new tests are passing.

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dev/devicelab/bin/run.dart

@@ -38,6 +38,11 @@ Future<void> main(List<String> rawArgs) async {
   /// Required for A/B test mode.
   final String? localEngine = args['local-engine'] as String?;
 
+  /// The build of the local Web SDK to use.
+  ///
+  /// Required for A/B test mode.
+  final String? localWebSdk = args['local-web-sdk'] as String?;
+
   /// The path to the engine "src/" directory.
   final String? localEngineSrcPath = args['local-engine-src-path'] as String?;
 
@@ -85,8 +90,8 @@ Future<void> main(List<String> rawArgs) async {
       stderr.writeln(argParser.usage);
       exit(1);
     }
-    if (localEngine == null) {
-      stderr.writeln('When running in A/B test mode --local-engine is required.\n');
+    if (localEngine == null && localWebSdk == null) {
+      stderr.writeln('When running in A/B test mode --local-engine or --local-web-sdk is required.\n');
       stderr.writeln(argParser.usage);
       exit(1);
     }
@@ -94,6 +99,7 @@ Future<void> main(List<String> rawArgs) async {
       runsPerTest: runsPerTest,
       silent: silent,
       localEngine: localEngine,
+      localWebSdk: localWebSdk,
       localEngineSrcPath: localEngineSrcPath,
       deviceId: deviceId,
       resultsFile: resultsFile,
@@ -118,7 +124,8 @@ Future<void> main(List<String> rawArgs) async {
 Future<void> _runABTest({
   required int runsPerTest,
   required bool silent,
-  required String localEngine,
+  required String? localEngine,
+  required String? localWebSdk,
   required String? localEngineSrcPath,
   required String? deviceId,
   required String resultsFile,
@@ -126,7 +133,9 @@ Future<void> _runABTest({
 }) async {
   print('$taskName A/B test. Will run $runsPerTest times.');
 
-  final ABTest abTest = ABTest(localEngine, taskName);
+  assert(localEngine != null || localWebSdk != null);
+
+  final ABTest abTest = ABTest((localEngine ?? localWebSdk)!, taskName);
   for (int i = 1; i <= runsPerTest; i++) {
     section('Run #$i');
 
@@ -152,6 +161,7 @@ Future<void> _runABTest({
       taskName,
       silent: silent,
       localEngine: localEngine,
+      localWebSdk: localWebSdk,
       localEngineSrcPath: localEngineSrcPath,
       deviceId: deviceId,
     );
@@ -282,6 +292,14 @@ ArgParser createArgParser(List<String> taskNames) {
             'This path is relative to --local-engine-src-path/out. This option\n'
             'is required when running an A/B test (see the --ab option).',
     )
+    ..addOption(
+      'local-web-sdk',
+      help: 'Name of a build output within the engine out directory, if you\n'
+            'are building Flutter locally. Use this to select a specific\n'
+            'version of the engine if you have built multiple engine targets.\n'
+            'This path is relative to --local-engine-src-path/out. This option\n'
+            'is required when running an A/B test (see the --ab option).',
+    )
     ..addFlag(
       'list',
       abbr: 'l',

dev/devicelab/lib/framework/runner.dart

@@ -153,6 +153,7 @@ Future<TaskResult> runTask(
   bool terminateStrayDartProcesses = false,
   bool silent = false,
   String? localEngine,
+  String? localWebSdk,
   String? localEngineSrcPath,
   String? deviceId,
   List<String>? taskArgs,
@@ -181,6 +182,7 @@ Future<TaskResult> runTask(
       '--enable-vm-service=0', // zero causes the system to choose a free port
       '--no-pause-isolates-on-exit',
       if (localEngine != null) '-DlocalEngine=$localEngine',
+      if (localWebSdk != null) '-DlocalWebSdk=$localWebSdk',
       if (localEngineSrcPath != null) '-DlocalEngineSrcPath=$localEngineSrcPath',
       taskExecutable,
       ...?taskArgs,

dev/devicelab/lib/framework/utils.dart

@@ -35,6 +35,14 @@ String? get localEngineSrcPathFromEnv {
   return isDefined ? const String.fromEnvironment('localEngineSrcPath') : null;
 }
 
+/// The local Web SDK to use for [flutter] and [evalFlutter], if any.
+///
+/// This is set as an environment variable when running the task, see runTask in runner.dart.
+String? get localWebSdkFromEnv {
+  const bool isDefined = bool.hasEnvironment('localWebSdk');
+  return isDefined ? const String.fromEnvironment('localWebSdk') : null;
+}
+
 List<ProcessInfo> _runningProcesses = <ProcessInfo>[];
 ProcessManager _processManager = const LocalProcessManager();
 
@@ -446,6 +454,7 @@ List<String> _flutterCommandArgs(String command, List<String> options) {
   };
   final String? localEngine = localEngineFromEnv;
   final String? localEngineSrcPath = localEngineSrcPathFromEnv;
+  final String? localWebSdk = localWebSdkFromEnv;
   return <String>[
     command,
     if (deviceOperatingSystem == DeviceOperatingSystem.ios && supportedDeviceTimeoutCommands.contains(command))
@@ -460,6 +469,7 @@ List<String> _flutterCommandArgs(String command, List<String> options) {
     ],
     if (localEngine != null) ...<String>['--local-engine', localEngine],
     if (localEngineSrcPath != null) ...<String>['--local-engine-src-path', localEngineSrcPath],
+    if (localWebSdk != null) ...<String>['--local-web-sdk', localWebSdk],
     ...options,
   ];
 }

dev/devicelab/lib/tasks/perf_tests.dart

@@ -1192,6 +1192,7 @@ class WebCompileTest {
     return inDirectory<Map<String, int>>(directory, () async {
       final Map<String, int> metrics = <String, int>{};
 
+      await flutter('clean');
       await flutter('packages', options: <String>['get']);
       final Stopwatch? watch = measureBuildTime ? Stopwatch() : null;
       watch?.start();
@@ -1200,6 +1201,7 @@ class WebCompileTest {
         '-v',
         '--release',
         '--no-pub',
+        '--no-web-resources-cdn',
       ]);
       watch?.stop();
       final String buildDir = path.join(directory, 'build', 'web');

dev/devicelab/lib/tasks/web_benchmarks.dart

@@ -25,11 +25,13 @@ Future<TaskResult> runWebBenchmark({ required bool useCanvasKit }) async {
   Logger.root.level = Level.INFO;
   final String macrobenchmarksDirectory = path.join(flutterDirectory.path, 'dev', 'benchmarks', 'macrobenchmarks');
   return inDirectory(macrobenchmarksDirectory, () async {
+    await flutter('clean');
     await evalFlutter('build', options: <String>[
       'web',
       '--dart-define=FLUTTER_WEB_ENABLE_PROFILING=true',
       '--web-renderer=${useCanvasKit ? 'canvaskit' : 'html'}',
       '--profile',
+      '--no-web-resources-cdn',
       '-t',
       'lib/web_benchmarks.dart',
     ]);