Add a missing copyright notice.

pkg/front_end/lib/src/base/library_info.dart

Index: pkg/front_end/lib/src/base/library_info.dart
diff --git a/pkg/front_end/lib/src/base/library_info.dart b/pkg/front_end/lib/src/base/library_info.dart
index 35494541d83bc68035b60c8fd50d87fac6977b58..a66b6d540226f92807a7f5cf763f6e9db74ad82c 100644
--- a/pkg/front_end/lib/src/base/library_info.dart
+++ b/pkg/front_end/lib/src/base/library_info.dart
@@ -1,3 +1,7 @@
+// Copyright (c) 2017, 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.
+
 /// A bit flag used by [LibraryInfo] indicating that a library is used by
 /// dart2js.
 ///