Check implicit super call in synthetic constructor.

tests/language/constructor10_test.dart

+// Copyright (c) 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.
+
+// Check that the implicit super call for synthetic constructors are checked.
+
+
+class A {
+  final x;
+  A(this.x);
+}
+
+class B extends A {
+  /*  /// 00: compile-time error
+  B() : super(null);
+  */  /// 00: continued
+}
+
+// ==========
+
+class Y extends A {
+  /*  /// 01: compile-time error
+  Y() : super(null);
+  */  /// 01: continued
+}
+
+class Z extends Y {
+  Z() : super();
+}
+
+// ==============
+
+class G extends A {
+  /*  /// 02: compile-time error
+  G() : super(null);
+  */  /// 02: continued
+}
+
+class H extends G {
+}
+
+main() {
+  new B().x;
+  new Z().x;
+  new H().x;
+}