Record the dependency of a implicit constructor to its superclass.

sdk/lib/_internal/compiler/implementation/world.dart

 // 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.
 
 part of dart2js;
 
 class World {
   final Compiler compiler;
   final FunctionSet allFunctions;
   final Set<Element> functionsCalledInLoop = new Set<Element>();
@@ skipping 255 matching lines @@
     return sideEffects;
   }
 
   void registerCannotThrow(Element element) {
     elementsThatCannotThrow.add(element);
   }
 
   bool getCannotThrow(Element element) {
     return elementsThatCannotThrow.contains(element);
   }
+
+  void registerImplicitSuperCall(TreeElements elements,
+                                 FunctionElement superConstructor) {
+    elements.otherDependencies.add(superConstructor);
+  }
 }