[dart2js] Update build infrastructure to move Dart2JS onto sound null safety.

Change-Id: Id172ab72e5d36899f699bb48f8ceb3609964efbc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/280221
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Nate Biggs <natebiggs@google.com>

pkg/compiler/test/end_to_end/dart2js_batch_test.dart

@@ -65,9 +65,8 @@ Future runTests(Process process) {
   String outFile = path.join(tmpDir.path, 'out.js');
   String outFile2 = path.join(tmpDir.path, 'out2.js');
 
-  // TODO(48820): remove null safety flag.
-  process.stdin.writeln('--no-sound-null-safety --out="$outFile" "$inFile"');
-  process.stdin.writeln('--no-sound-null-safety --out="$outFile2" "$inFile"');
+  process.stdin.writeln('--out="$outFile" "$inFile"');
+  process.stdin.writeln('--out="$outFile2" "$inFile"');
   process.stdin.writeln('too many arguments');
   process.stdin.writeln(r'"nonexistent file.dart"');
   process.stdin.close();

pkg/dartdev/lib/src/commands/compile.dart

@@ -79,7 +79,6 @@ class CompileJSCommand extends CompileSubcommandCommand {
         ...argResults!.arguments,
       ],
       packageConfigOverride: null,
-      forceNoSoundNullSafety: true,
     );
 
     return 0;

sdk/bin/dart2js

@@ -37,7 +37,6 @@ fi
 unset EXTRA_VM_OPTIONS
 declare -a EXTRA_VM_OPTIONS
 
-EXTRA_VM_OPTIONS+=('--no_sound_null_safety')
 case $0 in
   *_developer)
     EXTRA_VM_OPTIONS+=('--enable-asserts')

utils/compiler/BUILD.gn

@@ -60,8 +60,7 @@ application_snapshot("dart2js") {
     "$root_out_dir/dart2js_outline.dill",
     "$root_out_dir/dart2js_outline_unsound.dill",
   ]
-  gen_kernel_args = [ "--no-sound-null-safety" ]
-  vm_args = [ "--no-sound-null-safety" ]
+  vm_args = []
   main_dart = "$target_gen_dir/dart2js.dart"
   training_args = [
     "--packages=" + rebase_path("../../.dart_tool/package_config.json"),
@@ -71,8 +70,6 @@ application_snapshot("dart2js") {
     # sources.
     "--platform-binaries=" + rebase_path("$root_out_dir/"),
 
-    # TODO(48820): remove once dart2js is migrated.
-    "--no-sound-null-safety",
     rebase_path("../../pkg/compiler/lib/src/util/memory_compiler.dart"),
   ]
 }

utils/compiler/create_snapshot_entry.dart

@@ -24,7 +24,6 @@ Future<String> getVersion(var rootPath) {
 Future<String> getDart2jsSnapshotGenerationFile(var rootPath) {
   return getVersion(rootPath).then((version) {
     var snapshotGenerationText = """
-// @dart = 2.9
 import 'package:compiler/src/dart2js.dart' as dart2jsMain;
 
 void main(List<String> arguments) {