add profile mode to flutter web applications (#39073)

packages/flutter_tools/lib/src/build_runner/build_script.dart

@@ -38,6 +38,8 @@ const String digestsEntrypointExtension = '.digests';
 const String jsModuleErrorsExtension = '.ddc.js.errors';
 const String jsModuleExtension = '.ddc.js';
 const String jsSourceMapExtension = '.ddc.js.map';
+const String kReleaseFlag = 'release';
+const String kProfileFlag = 'profile';
 
 final DartPlatform flutterWebPlatform =
     DartPlatform.register('flutter_web', <String>[
@@ -141,7 +143,8 @@ final List<core.BuilderApplication> builders = <core.BuilderApplication>[
     'flutter_tools:entrypoint',
     <BuilderFactory>[
       (BuilderOptions options) => FlutterWebEntrypointBuilder(
-          options.config['release'] ??  false,
+          options.config[kReleaseFlag] ?? false,
+          options.config[kProfileFlag] ?? false,
           options.config['flutterWebSdk'],
       ),
     ],
@@ -201,9 +204,10 @@ class FlutterWebTestEntrypointBuilder implements Builder {
 
 /// A ddc-only entrypoint builder that respects the Flutter target flag.
 class FlutterWebEntrypointBuilder implements Builder {
-  const FlutterWebEntrypointBuilder(this.release, this.flutterWebSdk);
+  const FlutterWebEntrypointBuilder(this.release, this.profile, this.flutterWebSdk);
 
   final bool release;
+  final bool profile;
   final String flutterWebSdk;
 
   @override
@@ -219,8 +223,8 @@ class FlutterWebEntrypointBuilder implements Builder {
 
   @override
   Future<void> build(BuildStep buildStep) async {
-    if (release) {
-      await bootstrapDart2Js(buildStep, flutterWebSdk);
+    if (release || profile) {
+      await bootstrapDart2Js(buildStep, flutterWebSdk, profile);
     } else {
       await bootstrapDdc(buildStep, platform: flutterWebPlatform);
     }
@@ -366,7 +370,7 @@ Future<void> main() async {
   };
 }
 
-Future<void> bootstrapDart2Js(BuildStep buildStep, String flutterWebSdk) async {
+Future<void> bootstrapDart2Js(BuildStep buildStep, String flutterWebSdk, bool profile) async {
   final AssetId dartEntrypointId = buildStep.inputId;
   final AssetId moduleId = dartEntrypointId.changeExtension(moduleExtension(flutterWebPlatform));
   final Module module = Module.fromJson(json.decode(await buildStep.readAsString(moduleId)));
@@ -388,11 +392,17 @@ Future<void> bootstrapDart2Js(BuildStep buildStep, String flutterWebSdk) async {
   final String librariesPath = path.join(flutterWebSdkPath, 'libraries.json');
   final List<String> args = <String>[
     '--libraries-spec="$librariesPath"',
-    '-O4',
+    if (profile)
+      '-O1'
+    else
+      '-O4',
     '-o',
     '$jsOutputPath',
     '--packages="$packageFile"',
-    '-Ddart.vm.product=true',
+    if (profile)
+      '-Ddart.vm.profile=true'
+    else
+      '-Ddart.vm.product=true',
     dartPath,
   ];
   final Dart2JsBatchWorkerPool dart2js = await buildStep.fetchResource(dart2JsWorkerResource);

packages/flutter_tools/lib/src/build_runner/web_fs.dart

@@ -140,7 +140,7 @@ class WebFs {
   }) async {
     // Start the build daemon and run an initial build.
     final BuildDaemonClient client = await buildDaemonCreator
-      .startBuildDaemon(fs.currentDirectory.path, release: buildInfo.isRelease);
+      .startBuildDaemon(fs.currentDirectory.path, release: buildInfo.isRelease, profile: buildInfo.isProfile);
     client.startBuild();
     // Only provide relevant build results
     final Stream<BuildResult> filteredBuildResults = client.buildResults
@@ -266,11 +266,12 @@ class BuildDaemonCreator {
   const BuildDaemonCreator();
 
   /// Start a build daemon and register the web targets.
-  Future<BuildDaemonClient> startBuildDaemon(String workingDirectory, {bool release = false}) async {
+  Future<BuildDaemonClient> startBuildDaemon(String workingDirectory, {bool release = false, bool profile = false }) async {
     try {
       final BuildDaemonClient client = await _connectClient(
         workingDirectory,
         release: release,
+        profile: profile,
       );
       _registerBuildTargets(client);
       return client;
@@ -297,7 +298,7 @@ class BuildDaemonCreator {
 
   Future<BuildDaemonClient> _connectClient(
     String workingDirectory,
-    { bool release }
+    { bool release, bool profile }
   ) {
     final String flutterToolsPackages = fs.path.join(Cache.flutterRoot, 'packages', 'flutter_tools', '.packages');
     final String buildScript = fs.path.join(Cache.flutterRoot, 'packages', 'flutter_tools', 'lib', 'src', 'build_runner', 'build_script.dart');
@@ -316,6 +317,7 @@ class BuildDaemonCreator {
         '--define', 'flutter_tools:ddc=flutterWebSdk=$flutterWebSdk',
         '--define', 'flutter_tools:entrypoint=flutterWebSdk=$flutterWebSdk',
         '--define', 'flutter_tools:entrypoint=release=$release',
+        '--define', 'flutter_tools:entrypoint=profile=$profile',
         '--define', 'flutter_tools:shell=flutterWebSdk=$flutterWebSdk',
       ],
       logHandler: (ServerLog serverLog) {