begin migrating //flutter/dev/tools to null-safety (#80834)

dev/tools/localization/bin/encode_kn_arb_files.dart

@@ -13,6 +13,8 @@
 // This utility is run by `gen_localizations.dart` if --overwrite is passed
 // in as an option.
 
+// @dart = 2.8
+
 import 'dart:convert';
 import 'dart:io';
 

dev/tools/localization/bin/gen_date_localizations.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 /// This program extracts localized date symbols and patterns from the intl
 /// package for the subset of locales supported by the flutter_localizations
 /// package.

dev/tools/localization/bin/gen_localizations.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // This program generates a getMaterialTranslation() and a
 // getCupertinoTranslation() function that look up the translations provided by
 // the arb files. The returned value is a generated instance of a

dev/tools/localization/bin/gen_missing_localizations.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 // This program updates the language locale arb files with any missing resource
 // entries that are included in the English arb files. This is useful when
 // adding new resources for localization. You can just add the appropriate

dev/tools/localization/gen_cupertino_localizations.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'localizations_utils.dart';
 
 String generateCupertinoHeader(String regenerateInstructions) {

dev/tools/localization/gen_material_localizations.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'localizations_utils.dart';
 
 String generateMaterialHeader(String regenerateInstructions) {

dev/tools/localization/localizations_utils.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:convert';
 import 'dart:io';
 

dev/tools/localization/localizations_validator.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// @dart = 2.8
+
 import 'dart:convert' show json;
 import 'dart:io';