Reduce use of elements/resolution_types in enqueuer.

pkg/compiler/lib/src/js_backend/mirrors_data.dart

 // Copyright (c) 2017, 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.
 
 import '../closure.dart';
 import '../common.dart';
 import '../common_elements.dart';
 import '../compiler.dart';
 import '../constants/values.dart';
 import '../elements/elements.dart';
@@ skipping 294 matching lines @@
             });
           }
         });
         // 4) all overriding members of subclasses/subtypes (should be resolved)
         if (closedWorld.hasAnyStrictSubtype(cls)) {
           closedWorld.forEachStrictSubtypeOf(cls, (ClassElement subcls) {
             subcls.forEachClassMember((Member member) {
               if (memberNames.contains(member.name)) {
                 // TODO(20993): find out why this assertion fails.
                 // assert(invariant(member.element,
-                //    resolution.hasBeenProcessed(member.element)));
+                //    worldBuilder.isMemberUsed(member.element)));
                 if (worldBuilder.isMemberUsed(member.element)) {
                   reflectableMembers.add(member.element);
                 }
               }
             });
           });
         }
         // 5) all its closures
         List<LocalFunctionElement> closures = closureMap[cls];
         if (closures != null) {
@@ skipping 85 matching lines @@
   }
 
   /// Called when [:const Symbol(name):] is seen.
   void registerConstSymbol(String name) {
     symbolsUsed.add(name);
     if (name.endsWith('=')) {
       symbolsUsed.add(name.substring(0, name.length - 1));
     }
   }
 }