Add NativeEnqueuer to work with the Enqueuer.

pkg/dartdoc/lib/src/mirrors/dart2js_mirror.dart

Index: pkg/dartdoc/lib/src/mirrors/dart2js_mirror.dart
diff --git a/pkg/dartdoc/lib/src/mirrors/dart2js_mirror.dart b/pkg/dartdoc/lib/src/mirrors/dart2js_mirror.dart
index 995fcba847fe79b97aece79b397dab25b53088d2..2baa4df55d3f703c9cccee748832f63df1bc7ad4 100644
--- a/pkg/dartdoc/lib/src/mirrors/dart2js_mirror.dart
+++ b/pkg/dartdoc/lib/src/mirrors/dart2js_mirror.dart
@@ -243,6 +243,9 @@ class LibraryCompiler extends api.Compiler {
 
     world.populate();
 
+    enqueuer.resolution.nativeEnqueuer =
+        backend.nativeResolutionEnqueuer(enqueuer.resolution);
+
     log('Resolving...');
     phase = Compiler.PHASE_RESOLVING;
     backend.enqueueHelpers(enqueuer.resolution);
@@ -251,7 +254,7 @@ 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);
@@ -1397,4 +1400,3 @@ class Dart2JsFieldMirror extends Dart2JsElementMirror
     }
   }
 }
-