Include superclasses of classes only needed for rti

pkg/compiler/lib/src/js_emitter/program_builder/program_builder.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.
 
 library dart2js.js_emitter.program_builder;
 
 import '../../closure.dart' show ClosureTask, ClosureFieldElement;
 import '../../common.dart';
 import '../../common/names.dart' show Names, Selectors;
 import '../../constants/values.dart'
@@ skipping 191 matching lines @@
     // We thus build the classes before building their containers.
     collector.outputClassLists
         .forEach((OutputUnit _, List<ClassElement> classes) {
       classes.forEach(_buildClass);
     });
 
     // Resolve the superclass references after we've processed all the classes.
     _classes.forEach((ClassElement element, Class c) {
       if (element.superclass != null) {
         c.setSuperclass(_classes[element.superclass]);
-        assert(c.superclass != null);
+        assert(invariant(element, c.superclass != null,
+            message: "No Class for has been created for superclass "
+                "${element.superclass} of $c."));
       }
       if (c is MixinApplication) {
         c.setMixinClass(_classes[computeMixinClass(element)]);
         assert(c.mixinClass != null);
       }
     });
 
     List<Class> nativeClasses = collector.nativeClassesAndSubclasses
         .map((ClassElement classElement) => _classes[classElement])
         .toList();
@@ skipping 871 matching lines @@
       Constant constant = new Constant(name, holder, constantValue);
       _constants[constantValue] = constant;
     }
   }
 
   Holder _registerStaticStateHolder() {
     return _registry.registerHolder(_namer.staticStateHolder,
         isStaticStateHolder: true);
   }
 }