[dart2wasm] Wire up cfe experimental flags.

Change-Id: Iab9b3a5997e63e61a42bc4fb27825b345ae63ab1
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/264060
Reviewed-by: Aske Simon Christensen <askesc@google.com>
Commit-Queue: Joshua Litt <joshualitt@google.com>
Reviewed-by: Jake Macdonald <jakemac@google.com>

pkg/dart2wasm/bin/dart2wasm.dart

@@ -8,6 +8,7 @@ import 'dart:typed_data';
 import 'package:args/args.dart' as args;
 import 'package:front_end/src/api_unstable/vm.dart'
     show printDiagnosticMessage, resolveInputUri;
+import 'package:front_end/src/api_unstable/vm.dart' as fe;
 
 import 'package:dart2wasm/compile.dart';
 import 'package:dart2wasm/compiler_options.dart';
@@ -51,9 +52,17 @@ final List<Option> options = [
       "watch", (o, values) => o.translatorOptions.watchPoints = values),
   StringMultiOption(
       "define", (o, values) => o.environment = processEnvironment(values),
-      abbr: "D")
+      abbr: "D"),
+  StringMultiOption("enable-experiment",
+      (o, values) => o.feExperimentalFlags = processFeExperimentalFlags(values))
 ];
 
+Map<fe.ExperimentalFlag, bool> processFeExperimentalFlags(
+        List<String> experiments) =>
+    fe.parseExperimentalFlags(fe.parseExperimentalArguments(experiments),
+        onError: (error) => throw ArgumentError(error),
+        onWarning: (warning) => print(warning));
+
 Map<String, String> processEnvironment(List<String> defines) =>
     Map<String, String>.fromEntries(defines.map((d) {
       List<String> keyAndValue = d.split('=');

pkg/dart2wasm/lib/compile.dart

@@ -48,6 +48,7 @@ Future<Uint8List?> compileToModule(compiler.CompilerOptions options,
     ..librariesSpecificationUri = options.librariesSpecPath
     ..packagesFileUri = options.packagesPath
     ..environmentDefines = options.environment
+    ..explicitExperimentalFlags = options.feExperimentalFlags
     ..verbose = false
     ..onDiagnostic = diagnosticMessageHandler
     ..nnbdMode = NnbdMode.Strong;

pkg/dart2wasm/lib/compiler_options.dart

@@ -5,6 +5,7 @@
 import 'dart:io';
 
 import 'package:dart2wasm/translator.dart';
+import 'package:front_end/src/api_unstable/vm.dart' as fe;
 
 class CompilerOptions {
   final TranslatorOptions translatorOptions = TranslatorOptions();
@@ -16,6 +17,7 @@ class CompilerOptions {
   Uri mainUri;
   String outputFile;
   Map<String, String> environment = const {};
+  Map<fe.ExperimentalFlag, bool> feExperimentalFlags = const {};
 
   factory CompilerOptions.defaultOptions() =>
       CompilerOptions(mainUri: Uri(), outputFile: '');

pkg/test_runner/lib/src/compiler_configuration.dart

@@ -529,6 +529,8 @@ class Dart2WasmCompilerConfiguration extends CompilerConfiguration {
       TestFile testFile, List<String> vmOptions, List<String> args) {
     return [
       ...testFile.sharedOptions,
+      ..._configuration.sharedOptions,
+      ..._experimentsArgument(_configuration, testFile),
       // The file being compiled is the last argument.
       args.last
     ];