Change Enqueuer to use Entity instead of Element.

pkg/compiler/lib/src/universe/world_impact.dart

 // Copyright (c) 2015, 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.universe.world_impact;
 
 import '../elements/elements.dart' show Element;
 import '../util/util.dart' show Setlet;
 import 'use.dart' show DynamicUse, StaticUse, TypeUse;
 
@@ skipping 243 matching lines @@
 
   const ImpactUseCase(this.name);
 
   String toString() => 'ImpactUseCase($name)';
 }
 
 /// Strategy used for processing [WorldImpact] object in various use cases.
 class ImpactStrategy {
   const ImpactStrategy();
 
-  /// Applies [impact] to [visitor] for the [impactUseCase] of [element].
-  void visitImpact(Element element, WorldImpact impact,
+  /// Applies [impact] to [visitor] for the [impactUseCase] of [impactSource].
+  void visitImpact(var impactSource, WorldImpact impact,
       WorldImpactVisitor visitor, ImpactUseCase impactUseCase) {
     // Apply unconditionally.
     impact.apply(visitor);
   }
 
   /// Notifies the strategy that no more impacts of [impactUseCase] will be
   /// applied.
   void onImpactUsed(ImpactUseCase impactUseCase) {
     // Do nothing.
   }
@@ skipping 36 matching lines @@
     }
   }
 
   @override
   void visitTypeUse(TypeUse use) {
     if (_visitTypeUse != null) {
       _visitTypeUse(use);
     }
   }
 }