Reduce use of elements/resolution_types in enqueuer.

tests/compiler/dart2js/analyze_unused_dart2js_test.dart

 // Copyright (c) 2013, 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.
 
 library analyze_unused_dart2js;
 
 import 'package:async_helper/async_helper.dart';
 
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/diagnostics/messages.dart';
@@ skipping 43 matching lines @@
       const {}, // WHITE_LIST
       mode: AnalysisMode.TREE_SHAKING,
       checkResults: checkResults));
 }
 
 bool checkResults(Compiler compiler, CollectingDiagnosticHandler handler) {
   var helperUri =
       currentDirectory.resolve('pkg/compiler/lib/src/helpers/helpers.dart');
   void checkLive(member) {
     if (member.isFunction) {
-      if (compiler.enqueuer.resolution.hasBeenProcessed(member)) {
+      if (compiler.resolutionWorldBuilder.isMemberUsed(member)) {
         compiler.reporter.reportHintMessage(member, MessageKind.GENERIC,
             {'text': "Helper function in production code '$member'."});
       }
     } else if (member.isClass) {
       if (member.isResolved) {
         compiler.reporter.reportHintMessage(member, MessageKind.GENERIC,
             {'text': "Helper class in production code '$member'."});
       } else {
         member.forEachLocalMember(checkLive);
       }
     } else if (member.isTypedef) {
       if (member.isResolved) {
         compiler.reporter.reportHintMessage(member, MessageKind.GENERIC,
             {'text': "Helper typedef in production code '$member'."});
       }
     }
   }
 
   compiler.libraryLoader.lookupLibrary(helperUri).forEachLocalMember(checkLive);
   return handler.checkResults();
 }