Introduce isAbstractlyInstantiated to avoid exact masks of abstract classes.

tests/compiler/dart2js/class_set_test.dart

 // Copyright (c) 2015, 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.
 
 // Test for iterators on for [SubclassNode].
 
 library class_set_test;
 
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
@@ skipping 511 matching lines @@
 
   checkForEach(X, [X, A, B, D, C, G, F, I, H, E], forEachSubtype: true);
   checkForEach(X, [X, A, B, D], stop: D, forEachSubtype: true);
   checkForEach(X, [X, A, B, D, C, G, F, E],
       skipSubclasses: [F], forEachSubtype: true);
   checkForEach(X, [X, A, B, D, C, G, F, I, H, E],
       skipSubclasses: [X], forEachSubtype: true);
   checkForEach(X, [X, A, B, D, C, G, F, I, H, E],
       skipSubclasses: [D], forEachSubtype: true);
   checkForEach(X, [A, D, C, G, F, I, H, E],
-      forEachSubtype: true, mask: ClassHierarchyNode.DIRECTLY_INSTANTIATED);
+      forEachSubtype: true, mask: ClassHierarchyNode.EXPLICITLY_INSTANTIATED);
   checkForEach(X, [A, B, D, C, G, F, I, H, E],
       forEachSubtype: true, mask: ClassHierarchyNode.INSTANTIATED);
 
   void checkAny(ClassElement cls, List<ClassElement> expected,
       {ClassElement find, bool expectedResult, bool anySubtype: false}) {
     ClassSet classSet = world.getClassSet(cls);
     List<ClassElement> visited = <ClassElement>[];
 
     bool visit(ClassElement cls) {
       visited.add(cls);
@@ skipping 33 matching lines @@
   checkAny(B, [B, D], find: D, anySubtype: true, expectedResult: true);
   checkAny(B, [B, D, F, I], find: I, anySubtype: true, expectedResult: true);
 
   checkAny(X, [X, A, B, D, C, G, F, I, H, E],
       anySubtype: true, expectedResult: false);
   checkAny(X, [X, A], find: A, anySubtype: true, expectedResult: true);
   checkAny(X, [X, A, B, D], find: D, anySubtype: true, expectedResult: true);
   checkAny(X, [X, A, B, D, C, G, F, I],
       find: I, anySubtype: true, expectedResult: true);
 }