Add NativeEnqueuer to work with the Enqueuer.

sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.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.
 
 library mirrors_dart2js;
 
 import 'dart:io';
 import 'dart:uri';
 
 import '../../compiler.dart' as diagnostics;
@@ skipping 247 matching lines @@
     world.populate();
 
     log('Resolving...');
     phase = Compiler.PHASE_RESOLVING;
     backend.enqueueHelpers(enqueuer.resolution);
     processQueueList(enqueuer.resolution, elementList);
     log('Resolved ${enqueuer.resolution.resolvedElements.length} elements.');
   }
 
   void processQueueList(Enqueuer world, List<LibraryElement> elements) {
-    backend.processNativeClasses(world, libraries.values);
+    world.nativeEnqueuer.processNativeClasses(libraries.values);
     for (var library in elements) {
       library.forEachLocalMember((element) {
         world.addToWorkList(element);
       });
     }
     progress.reset();
     world.forEach((WorkItem work) {
       withCurrentElement(work.element, () => work.run(this, world));
     });
   }
@@ skipping 1266 matching lines @@
     var node = _variable.variables.parseNode(_diagnosticListener);
     if (node != null) {
       var span = mirrors.compiler.spanFromNode(node, script.uri);
       return new Dart2JsSourceLocation(script, span);
     } else {
       var span = mirrors.compiler.spanFromElement(_variable);
       return new Dart2JsSourceLocation(script, span);
     }
   }
 }
-