Serve benchmarks with COOP/COEP headers in wasm mode. (flutter#7423)

We need `crossOriginIsolated` for skwasm to work. Otherwise, this just falls back and benchmarks JS + canvaskit.

packages/web_benchmarks/CHANGELOG.md

@@ -1,6 +1,9 @@
-## NEXT
+## 2.0.2
 
 * Updates minimum supported SDK version to Flutter 3.19/Dart 3.3.
+* Updates benchmark server to serve the app as `crossOriginIsolated`. This
+allows us access to high precision timers and allows wasm benchmarks to run
+properly as well.
 
 ## 2.0.1
 

packages/web_benchmarks/lib/src/runner.dart

@@ -160,10 +160,26 @@ class BenchmarkServer {
     Cascade cascade = Cascade();
 
     // Serves the static files built for the app (html, js, images, fonts, etc)
-    cascade = cascade.add(createStaticHandler(
+    final Handler buildFolderHandler = createStaticHandler(
       path.join(benchmarkAppDirectory.path, 'build', 'web'),
       defaultDocument: 'index.html',
-    ));
+    );
+    // We want our page to be crossOriginIsolated. This will allow us to run the
+    // skwasm renderer, which uses a SharedArrayBuffer, which requires the page
+    // to be crossOriginIsolated. But also, even in the non-skwasm case, running
+    // in crossOriginIsolated gives us access to more accurate timers which are
+    // useful for capturing good benchmarking data.
+    // See https://developer.mozilla.org/en-US/docs/Web/API/Performance_API/High_precision_timing#reduced_precision
+    cascade = cascade.add((Request request) async {
+      final Response response = await buildFolderHandler(request);
+      if (response.mimeType == 'text/html') {
+        return response.change(headers: <String, String>{
+          'Cross-Origin-Opener-Policy': 'same-origin',
+          'Cross-Origin-Embedder-Policy': 'require-corp',
+        });
+      }
+      return response;
+    });
 
     // Serves the benchmark server API used by the benchmark app to coordinate
     // the running of benchmarks.

packages/web_benchmarks/pubspec.yaml

@@ -2,7 +2,7 @@ name: web_benchmarks
 description: A benchmark harness for performance-testing Flutter apps in Chrome.
 repository: https://github.com/flutter/packages/tree/main/packages/web_benchmarks
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+web_benchmarks%22
-version: 2.0.1
+version: 2.0.2
 
 environment:
   sdk: ^3.3.0

packages/web_benchmarks/testing/test_app/lib/benchmarks/runner_simple.dart

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:web_benchmarks/client.dart';
 
@@ -12,7 +13,11 @@ class SimpleRecorder extends AppRecorder {
 
   @override
   Future<void> automate() async {
-    // Do nothing.
+    // Record whether we are in wasm mode or not. Ideally, we'd have a more
+    // first-class way to add metadata like this, but this will work for us to
+    // pass information about the environment back to the server for the
+    // purposes of our own tests.
+    profile.extraData['isWasm'] = kIsWasm ? 1 : 0;
   }
 }
 

packages/web_benchmarks/testing/web_benchmarks_test.dart

@@ -19,27 +19,45 @@ Future<void> main() async {
   }, timeout: Timeout.none);
 
   test('Can run a web benchmark with an alternate initial page', () async {
-    await _runBenchmarks(
+    final BenchmarkResults results = await _runBenchmarks(
       benchmarkNames: <String>['simple'],
       entryPoint: 'lib/benchmarks/runner_simple.dart',
       initialPage: 'index.html#about',
     );
+
+    // The simple runner just puts an `isWasm` metric in there so we can make
+    // sure that we're running in the right environment.
+    final List<BenchmarkScore>? scores = results.scores['simple'];
+    expect(scores, isNotNull);
+
+    final BenchmarkScore isWasmScore =
+        scores!.firstWhere((BenchmarkScore score) => score.metric == 'isWasm');
+    expect(isWasmScore.value, 0);
   }, timeout: Timeout.none);
 
   test(
     'Can run a web benchmark with wasm',
     () async {
-      await _runBenchmarks(
+      final BenchmarkResults results = await _runBenchmarks(
         benchmarkNames: <String>['simple'],
         entryPoint: 'lib/benchmarks/runner_simple.dart',
         compilationOptions: const CompilationOptions.wasm(),
       );
+
+      // The simple runner just puts an `isWasm` metric in there so we can make
+      // sure that we're running in the right environment.
+      final List<BenchmarkScore>? scores = results.scores['simple'];
+      expect(scores, isNotNull);
+
+      final BenchmarkScore isWasmScore = scores!
+          .firstWhere((BenchmarkScore score) => score.metric == 'isWasm');
+      expect(isWasmScore.value, 1);
     },
     timeout: Timeout.none,
   );
 }
 
-Future<void> _runBenchmarks({
+Future<BenchmarkResults> _runBenchmarks({
   required List<String> benchmarkNames,
   required String entryPoint,
   String initialPage = defaultInitialPage,
@@ -53,12 +71,17 @@ Future<void> _runBenchmarks({
     compilationOptions: compilationOptions,
   );
 
+  // The skwasm renderer doesn't have preroll or apply frame steps in its rendering.
+  final List<String> expectedMetrics = compilationOptions.useWasm
+      ? <String>['drawFrameDuration']
+      : <String>[
+          'preroll_frame',
+          'apply_frame',
+          'drawFrameDuration',
+        ];
+
   for (final String benchmarkName in benchmarkNames) {
-    for (final String metricName in <String>[
-      'preroll_frame',
-      'apply_frame',
-      'drawFrameDuration',
-    ]) {
+    for (final String metricName in expectedMetrics) {
       for (final String valueName in <String>[
         'average',
         'outlierAverage',
@@ -83,4 +106,5 @@ Future<void> _runBenchmarks({
     const JsonEncoder.withIndent('  ').convert(taskResult.toJson()),
     isA<String>(),
   );
+  return taskResult;
 }