Make it possible to generate headers with the correct year

pkg/analyzer/lib/src/codegen/tools.dart

Index: pkg/analyzer/lib/src/codegen/tools.dart
diff --git a/pkg/analyzer/lib/src/codegen/tools.dart b/pkg/analyzer/lib/src/codegen/tools.dart
index cccab10ce4abda6d4e009be9d8dc2f2345fab25a..da7181287fb0fd7f616199672d78a3e01680cd82 100644
--- a/pkg/analyzer/lib/src/codegen/tools.dart
+++ b/pkg/analyzer/lib/src/codegen/tools.dart
@@ -155,12 +155,12 @@ class CodeGenerator {
     });
   }
 
-  void outputHeader({bool javaStyle: false}) {
+  void outputHeader({bool javaStyle: false, String year = null}) {
     String header;
     if (codeGeneratorSettings.languageName == 'java') {
       header = '''
 /*
- * Copyright (c) 2015, the Dart project authors.
+ * Copyright (c) ${year ?? '2015'}, the Dart project authors.
  *
  * Licensed under the Eclipse Public License v1.0 (the "License"); you may not use this file except
  * in compliance with the License. You may obtain a copy of the License at
@@ -177,7 +177,7 @@ class CodeGenerator {
  */''';
     } else if (codeGeneratorSettings.languageName == 'python') {
       header = '''
-# Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+# Copyright (c) ${year ?? '2014'}, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 #
@@ -187,7 +187,7 @@ class CodeGenerator {
 ''';
     } else {
       header = '''
-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) ${year ?? '2014'}, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //