dart2js: use WorldImpact for dump_info

pkg/compiler/lib/src/enqueue.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 dart2js.enqueue;
 
 import 'dart:collection' show
     Queue;
 
 import 'common.dart';
@@ skipping 870 matching lines @@
 
   void forgetElement(Element element) {
     super.forgetElement(element);
     processedElements.remove(element);
   }
 }
 
 /// [Enqueuer] which is specific to code generation.
 class CodegenEnqueuer extends Enqueuer {
   final Queue<CodegenWorkItem> queue;
-  final Map<Element, js.Expression> generatedCode =
-      new Map<Element, js.Expression>();
+  final Map<Element, js.Expression> generatedCode = <Element, js.Expression>{};
 
   final Set<Element> newlyEnqueuedElements;
 
   final Set<DynamicUse> newlySeenSelectors;
 
   bool enabledNoSuchMethod = false;
 
   CodegenEnqueuer(Compiler compiler,
                   ItemCompilationContext itemCompilationContextCreator(),
                   EnqueuerStrategy strategy)
@@ skipping 130 matching lines @@
   @override
   void processStaticUse(Enqueuer enqueuer, StaticUse staticUse) {
     enqueuer.registerStaticUseInternal(staticUse);
   }
 
   @override
   void processDynamicUse(Enqueuer enqueuer, DynamicUse dynamicUse) {
     enqueuer.handleUnseenSelectorInternal(dynamicUse);
   }
 }