Check overrides.

dart/lib/compiler/implementation/enqueue.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.
 
 class EnqueueTask extends CompilerTask {
   final Enqueuer codegen;
   final Enqueuer resolution;
 
   String get name() => 'Enqueue';
 
@@ skipping 201 matching lines @@
       }
     } else if (member.kind === ElementKind.SETTER) {
       if (universe.hasInvokedSetter(member, compiler)) {
         return addToWorkList(member);
       }
     }
   }
 
   void onRegisterInstantiatedClass(ClassElement cls) {
     task.measure(() {
-      while (cls !== null) {
-        if (seenClasses.contains(cls)) return;
+      // The class must be resolved to compute the set of all
+      // supertypes.
+      cls.ensureResolved(compiler);
+
+      for (Link<Type> supertypes = cls.allSupertypesAndSelf;
+           !supertypes.isEmpty(); supertypes = supertypes.tail) {
+        cls = supertypes.head.element;
+        if (seenClasses.contains(cls)) continue;
         seenClasses.add(cls);
         cls.ensureResolved(compiler);
-        cls.localMembers.forEach(processInstantiatedClassMember);
-        cls = cls.superclass;
+        if (!cls.isInterface()) {
+          cls.localMembers.forEach(processInstantiatedClassMember);
+        }
+        if (isResolutionQueue) {
+          compiler.resolver.checkMembers(cls);
+        }
       }
     });
   }
 
   void registerNewSelector(SourceString name,
                            Selector selector,
                            Map<SourceString, Set<Selector>> selectorsMap) {
     if (name != selector.name) {
       String message = "$name != ${selector.name} (${selector.kind})";
       compiler.internalError("Wrong selector name: $message.");
@@ skipping 102 matching lines @@
   void forEach(f(WorkItem work)) {
     while (!queue.isEmpty()) {
       do {
         f(queue.removeLast());
       } while (!queue.isEmpty());
       // TODO(ahe): we shouldn't register the field closure invocations here.
       registerFieldClosureInvocations();
     }
   }
 }