Add NativeEnqueuer to work with the Enqueuer.

lib/compiler/implementation/enqueue.dart

Index: lib/compiler/implementation/enqueue.dart
diff --git a/lib/compiler/implementation/enqueue.dart b/lib/compiler/implementation/enqueue.dart
index 6ac8d8f8fa1fce744fa567f3016d24a42f1a35e8..52d02738f1bf082633659a0c1436d02fcc9ad3ba 100644
--- a/lib/compiler/implementation/enqueue.dart
+++ b/lib/compiler/implementation/enqueue.dart
@@ -41,6 +41,8 @@ class Enqueuer {
   bool queueIsClosed = false;
   EnqueueTask task;
 
+  NativeEnqueuer nativeEnqueuer;  // Set by compiler.
+
   Enqueuer(this.name, this.compiler,
            ItemCompilationContext itemCompilationContextCreator())
     : this.itemCompilationContextCreator = itemCompilationContextCreator,
@@ -114,6 +116,8 @@ class Enqueuer {
         && library.uri.toString() == 'dart:isolate') {
       compiler.enableIsolateSupport(library);
     }
+
+    nativeEnqueuer.registerElement(element);
   }
 
   /**
@@ -295,6 +299,9 @@ class Enqueuer {
       }
       return false;
     });
+    // TODO(sra):
+    //  getter selectors on native fields call nativeEnqueuer.registerFieldLoad,
+    //  setter selector on native fields call nativeEnqueuer.registerFieldStore.
   }
 
   /**