Enqueue superclasses instead of supertypes.

pkg/compiler/lib/src/enqueue.dart

Index: pkg/compiler/lib/src/enqueue.dart
diff --git a/pkg/compiler/lib/src/enqueue.dart b/pkg/compiler/lib/src/enqueue.dart
index 6ad51775b4ac6b19960671dd5d468bf98ac0e970..fb90b10ef215cd17b53b06755066386469cda022 100644
--- a/pkg/compiler/lib/src/enqueue.dart
+++ b/pkg/compiler/lib/src/enqueue.dart
@@ -194,7 +194,13 @@ abstract class Enqueuer {
       ClassElement cls = type.element;
       registry.registerDependency(cls);
       cls.ensureResolved(compiler);
-      universe.registerTypeInstantiation(type, byMirrors: mirrorUsage);
+      universe.registerTypeInstantiation(
+          type,
+          byMirrors: mirrorUsage,
+          onImplemented: (ClassElement cls) {
+        compiler.backend.registerImplementedClass(
+                    cls, this, compiler.globalDependencies);
+      });
       processInstantiatedClass(cls);
       compiler.backend.registerInstantiatedType(type, registry);
     });
@@ -336,10 +342,9 @@ abstract class Enqueuer {
         compiler.backend.registerInstantiatedClass(
             cls, this, compiler.globalDependencies);
       }
-      processClass(cls);
-      for (Link<DartType> supertypes = cls.allSupertypes;
-           !supertypes.isEmpty; supertypes = supertypes.tail) {
-        processClass(supertypes.head.element);
+      while (cls != null) {
+        processClass(cls);
+        cls = cls.superclass;
       }
     });
   }