Add test.

tests/language/src/LibraryPrivateInConstructorB.dart

Index: tests/language/src/LibraryPrivateInConstructorB.dart
diff --git a/tests/language/src/LibraryPrivateInConstructorB.dart b/tests/language/src/LibraryPrivateInConstructorB.dart
new file mode 100644
index 0000000000000000000000000000000000000000..c3d0fdae0c87a8e16edab7b5a01d21aa82bea8e8
--- /dev/null
+++ b/tests/language/src/LibraryPrivateInConstructorB.dart
@@ -0,0 +1,18 @@
+// Copyright (c) 2012, 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.
+
+#library('LibraryPrivateInConstructorB');
+#import("LibraryPrivateInConstructorA.dart");
+
+class PrivateB {
+  const PrivateB();
+  final _val = 42;
+}
+
+var fooB = const PrivateB();
+
+class B extends A {
+  var y;
+  B() : this.y = fooB._val;
+}