[pigeon] added dart version annotations until pigeon is migrated (#243)

packages/pigeon/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.1.15
+
+* Added support for running in versions of Dart that support NNBD.
+
 ## 0.1.14
 
 * [Windows] Fixed executing from drives other than C:.

packages/pigeon/bin/pigeon.dart

@@ -1,7 +1,7 @@
 // Copyright 2020 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-
+// @dart = 2.2
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
@@ -34,6 +34,7 @@ Future<void> main(List<String> args) async {
     importLine = 'import \'$relInputPath\';\n';
   }
   final String code = """$importLine
+// @dart = 2.2
 import 'dart:io';
 import 'dart:isolate';
 import 'package:pigeon/pigeon_lib.dart';

packages/pigeon/lib/generator_tools.dart

@@ -8,7 +8,7 @@ import 'dart:mirrors';
 import 'ast.dart';
 
 /// The current version of pigeon.
-const String pigeonVersion = '0.1.14';
+const String pigeonVersion = '0.1.15';
 
 /// Read all the content from [stdin] to a String.
 String readStdin() {

packages/pigeon/pubspec.yaml

@@ -1,5 +1,5 @@
 name: pigeon
-version: 0.1.14
+version: 0.1.15
 description: Code generator tool to make communication between Flutter and the host platform type-safe and easier.
 homepage: https://github.com/flutter/packages/tree/master/packages/pigeon
 dependencies: