Revert "Enqueue superclasses instead of supertypes."

pkg/compiler/lib/src/ssa/codegen.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 ssa;
 
 class SsaCodeGeneratorTask extends CompilerTask {
 
   final JavaScriptBackend backend;
   final SourceInformationStrategy sourceInformationFactory;
@@ skipping 1580 matching lines @@
 
   TypeMask getOptimizedSelectorFor(HInvokeDynamic node,
                                    Selector selector,
                                    TypeMask mask) {
     if (node.element != null) {
       // Create an artificial type mask to make sure only
       // [node.element] will be enqueued. We're not using the receiver
       // type because our optimizations might end up in a state where the
       // invoke dynamic knows more than the receiver.
       ClassElement enclosing = node.element.enclosingClass;
-      if (compiler.world.isInstantiated(enclosing)) {
-        return new TypeMask.nonNullExact(
-            enclosing.declaration, compiler.world);
-      } else {
-        // The element is mixed in so a non-null subtype mask is the most
-        // precise we have.
-        assert(invariant(node, compiler.world.isUsedAsMixin(enclosing),
-            message: "Element ${node.element} from $enclosing expected "
-                     "to be mixed in."));
-        return new TypeMask.nonNullSubtype(
-            enclosing.declaration, compiler.world);
-      }
+      return
+          new TypeMask.nonNullExact(enclosing.declaration, compiler.world);
     }
     // If [JSInvocationMirror._invokeOn] is enabled, and this call
     // might hit a `noSuchMethod`, we register an untyped selector.
     return compiler.world.extendMaskIfReachesAll(selector, mask);
   }
 
   void registerMethodInvoke(HInvokeDynamic node) {
     Selector selector = node.selector;
     TypeMask mask = getOptimizedSelectorFor(node, selector, node.mask);
 
@@ skipping 1250 matching lines @@
     }
     registry.registerStaticUse(helper);
     return backend.emitter.staticFunctionAccess(helper);
   }
 
   @override
   void visitRef(HRef node) {
     visit(node.value);
   }
 }