Enqueue superclasses instead of supertypes.

pkg/compiler/lib/src/resolution/registry.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.resolution.registry;
 
 import '../common/backend_api.dart' show
     Backend;
 import '../common/registry.dart' show
     Registry;
@@ skipping 76 matching lines @@
   void registerInstantiation(InterfaceType type) {
     // TODO(johnniwinther): Remove the need for passing `this`.
     world.registerInstantiatedType(type, this);
   }
 
   @override
   void registerStaticInvocation(Element element) {
     registerDependency(element);
     world.registerStaticUse(element);
   }
+
+  String toString() => 'EagerRegistry for ${mapping.analyzedElement}';
 }
 
 class ResolutionWorldImpact implements WorldImpact {
   final Registry registry;
   Setlet<UniverseSelector> _dynamicInvocations;
   Setlet<UniverseSelector> _dynamicGetters;
   Setlet<UniverseSelector> _dynamicSetters;
   Setlet<InterfaceType> _instantiatedTypes;
   Setlet<Element> _staticUses;
   Setlet<DartType> _checkedTypes;
@@ skipping 108 matching lines @@
         this.worldImpact = new ResolutionWorldImpact(compiler, mapping);
 
   bool get isForResolution => true;
 
   ResolutionEnqueuer get world => compiler.enqueuer.resolution;
 
   World get universe => compiler.world;
 
   Backend get backend => compiler.backend;
 
+  String toString() => 'ResolutionRegistry for ${mapping.analyzedElement}';
+
   //////////////////////////////////////////////////////////////////////////////
   //  Node-to-Element mapping functionality.
   //////////////////////////////////////////////////////////////////////////////
 
   /// Register [node] as the declaration of [element].
   void defineFunction(FunctionExpression node, FunctionElement element) {
     // TODO(sigurdm): Remove when not needed by the dart2dart backend.
     if (node.name != null) {
       mapping[node.name] = element;
     }
@@ skipping 371 matching lines @@
   }
 
   void registerIncDecOperation() {
     backend.resolutionCallbacks.onIncDecOperation(this);
   }
 
   void registerTryStatement() {
     mapping.containsTryStatement = true;
   }
 }