dart2js cleanup: remove unused imports and variables

pkg/compiler/lib/src/native/enqueue.dart

 // Copyright (c) 2014, 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.
 
 import 'dart:collection' show Queue;
 
 import '../common.dart';
 import '../common/backend_api.dart' show ForeignResolver;
 import '../common/registry.dart' show Registry;
-import '../common/resolution.dart' show Parsing, Resolution;
+import '../common/resolution.dart' show Resolution;
 import '../compiler.dart' show Compiler;
 import '../constants/values.dart';
 import '../core_types.dart' show CoreTypes;
 import '../dart_types.dart';
-import '../enqueue.dart' show Enqueuer, ResolutionEnqueuer;
 import '../elements/elements.dart';
-import '../elements/modelx.dart'
-    show BaseClassElementX, ElementX, FunctionElementX, LibraryElementX;
+import '../elements/modelx.dart' show FunctionElementX;
+import '../enqueue.dart' show Enqueuer;
 import '../js_backend/backend_helpers.dart' show BackendHelpers;
 import '../js_backend/js_backend.dart';
 import '../js_emitter/js_emitter.dart' show CodeEmitterTask, NativeEmitter;
 import '../tokens/token.dart' show BeginGroupToken, Token;
-import '../tokens/token_constants.dart' as Tokens show EOF_TOKEN, STRING_TOKEN;
+import '../tokens/token_constants.dart' as Tokens show EOF_TOKEN;
 import '../tree/tree.dart';
-
 import 'behavior.dart';
 
 /**
  * This could be an abstract class but we use it as a stub for the dart_backend.
  */
 class NativeEnqueuer {
   /// Initial entry point to native enqueuer.
   void processNativeClasses(Iterable<LibraryElement> libraries) {}
 
   /// Registers the [nativeBehavior]. Adds the liveness of its instantiated
@@ skipping 674 matching lines @@
     List<Element> directSubtypes =
         emitter.directSubtypes.putIfAbsent(superclass, () => <ClassElement>[]);
     directSubtypes.add(cls);
   }
 
   void logSummary(log(message)) {
     log('Compiled ${registeredClasses.length} native classes, '
         '${unusedClasses.length} native classes omitted.');
   }
 }