Include superclasses of classes only needed for rti

pkg/compiler/lib/src/js_emitter/program_builder/collector.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.
 
 part of dart2js.js_emitter.program_builder;
 
 /**
  * Generates the code for all used classes in the program. Static fields (even
  * in classes) are ignored, since they can be treated as non-class elements.
  *
@@ skipping 222 matching lines @@
         .toSet();
     neededClasses.addAll(mixinClasses);
 
     // 3. Find all classes needed for rti.
     // It is important that this is the penultimate step, at this point,
     // neededClasses must only contain classes that have been resolved and
     // codegen'd. The rtiNeededClasses may contain additional classes, but
     // these are thought to not have been instantiated, so we neeed to be able
     // to identify them later and make sure we only emit "empty shells" without
     // fields, etc.
-    classesOnlyNeededForRti = _rtiNeededClasses.difference(neededClasses);
+    classesOnlyNeededForRti = new Set<ClassElement>();
+    for (ClassElement cls in _rtiNeededClasses) {
+      while (cls != null && !neededClasses.contains(cls)) {
+        if (!classesOnlyNeededForRti.add(cls)) break;
+        cls = cls.superclass;
+      }
+    }
 
     neededClasses.addAll(classesOnlyNeededForRti);
 
     // TODO(18175, floitsch): remove once issue 18175 is fixed.
     if (neededClasses.contains(_commonElements.jsIntClass)) {
       neededClasses.add(_commonElements.intClass);
     }
     if (neededClasses.contains(_commonElements.jsDoubleClass)) {
       neededClasses.add(_commonElements.doubleClass);
     }
@@ skipping 88 matching lines @@
   }
 
   void collect() {
     computeNeededDeclarations();
     computeNeededConstants();
     computeNeededStatics();
     computeNeededStaticNonFinalFields();
     computeNeededLibraries();
   }
 }