Add NativeEnqueuer to work with the Enqueuer.

sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.dart

Index: sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.dart
diff --git a/sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.dart b/sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.dart
index fe4e6da855f1e3b705f00079eae712c329914f26..0cce3dbc31b043cc52f03a4f07972570c40842b1 100644
--- a/sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.dart
+++ b/sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.dart
@@ -245,6 +245,9 @@ class LibraryCompiler extends api.Compiler {
 
     world.populate();
 
+    enqueuer.resolution.nativeEnqueuer =
+        backend.nativeResolutionEnqueuer(enqueuer.resolution);
+
     log('Resolving...');
     phase = Compiler.PHASE_RESOLVING;
     backend.enqueueHelpers(enqueuer.resolution);
@@ -253,7 +256,7 @@ class LibraryCompiler extends api.Compiler {
   }
 
   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);
@@ -1536,4 +1539,3 @@ class Dart2JsFieldMirror extends Dart2JsMemberMirror implements VariableMirror {
     }
   }
 }
-