Use shared error for constructor's with return type.

pkg/dart_messages/lib/shared_messages.dart

 // Copyright (c) 2015, 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.
 
 // An update to this file must be followed by regenerating the corresponding
 // json, dart2js and analyzer file. Use `publish.dart` in the bin directory.
 //
 // Every message in this file must have an id. Use `message_id.dart` in the
 // bin directory to generate a fresh one.
 
@@ skipping 367 matching lines @@
         analyzer
       ],
       examples: const [
         "var const x = 499; main() {}",
         "const var x = 499; main() {}",
         "class A { var const x = 499; } main() {}",
         "class A { const var x = 499; } main() {}",
       ]),
 
   'CLASS_IN_CLASS': new Message(
+      // Dart2js currently reports this as an EXTRANEOUS_MODIFIER error.
+      // TODO(floitsch): make dart2js use this error instead.
       id: 'DOTHQH',
       category: Category.parserError,
       template: "Classes can't be declared inside other classes.",
       howToFix: "Try moving the class to the top-level.",
       usedBy: [analyzer],
-      examples: const ["class A { class B {} } main() {}",]),
+      examples: const ["class A { class B {} } main() { new A(); }",]),
 
   'CONSTRUCTOR_WITH_RETURN_TYPE': new Message(
       id: 'VOJBWY',
       category: Category.parserError,
       template: "Constructors can't have a return type",
       howToFix: "Try removing the return type.",
-      usedBy: [analyzer],
-      examples: const ["class A { int A() {} } main() {}",]),
+      usedBy: [analyzer, dart2js],
+      examples: const ["class A { int A() {} } main() { new A(); }",]),
 };