Reapply CL: first step for modular support in fasta

pkg/front_end/testcases/shaker/implicit_constructors.dart

Index: pkg/front_end/testcases/shaker/implicit_constructors.dart
diff --git a/pkg/front_end/testcases/shaker/implicit_constructors.dart b/pkg/front_end/testcases/shaker/implicit_constructors.dart
new file mode 100644
index 0000000000000000000000000000000000000000..1c3bd887eb8b4dcee9d1a53b938247b0a3dcc6ab
--- /dev/null
+++ b/pkg/front_end/testcases/shaker/implicit_constructors.dart
@@ -0,0 +1,9 @@
+// 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.md file.
+
+import 'lib/lib.dart';
+
+class D extends F {
+  D.x();
+}