Enqueue superclasses instead of supertypes.

pkg/compiler/lib/src/js_backend/backend.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 js_backend;
 
 const VERBOSE_OPTIMIZER_HINTS = false;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked = new Set<HInstruction>();
@@ skipping 1009 matching lines @@
                                 Registry registry) {
     assert(registry.isForResolution);
     ConstantValue constant = constants.getConstantValueForMetadata(metadata);
     registerCompileTimeConstant(constant, registry, addForEmission: false);
     metadataConstants.add(new Dependency(constant, annotatedElement));
   }
 
   void registerInstantiatedClass(ClassElement cls,
                                  Enqueuer enqueuer,
                                  Registry registry) {
+    _processClass(cls, enqueuer, registry);
+  }
+
+  void registerImplementedClass(ClassElement cls,
+                                Enqueuer enqueuer,
+                                Registry registry) {
+    _processClass(cls, enqueuer, registry);
+  }
+
+  void _processClass(ClassElement cls,
+                     Enqueuer enqueuer,
+                     Registry registry) {
     if (!cls.typeVariables.isEmpty) {
       typeVariableHandler.registerClassWithTypeVariables(cls, enqueuer,
                                                          registry);
     }
 
     // Register any helper that will be needed by the backend.
     if (enqueuer.isResolutionQueue) {
       if (cls == compiler.intClass
           || cls == compiler.doubleClass
           || cls == compiler.numClass) {
@@ skipping 2130 matching lines @@
   }
 }
 
 /// Records that [constant] is used by the element behind [registry].
 class Dependency {
   final ConstantValue constant;
   final Element annotatedElement;
 
   const Dependency(this.constant, this.annotatedElement);
 }