Decouple WorkItem from Compiler

pkg/compiler/lib/src/resolution/registry.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.
 
 library dart2js.resolution.registry;
 
 import '../common.dart';
 import '../common/backend_api.dart'
     show Backend, ForeignResolver, NativeRegistry;
 import '../common/resolution.dart' show ResolutionImpact, Target;
@@ skipping 18 matching lines @@
   final String name;
   EnumSet<Feature> _features;
   Setlet<MapLiteralUse> _mapLiterals;
   Setlet<ListLiteralUse> _listLiterals;
   Setlet<String> _constSymbolNames;
   Setlet<ConstantExpression> _constantLiterals;
   Setlet<dynamic> _nativeData;
 
   ResolutionWorldImpactBuilder(this.name);
 
+  @override
+  bool get isEmpty => false;
+
   void registerMapLiteral(MapLiteralUse mapLiteralUse) {
     assert(mapLiteralUse != null);
     if (_mapLiterals == null) {
       _mapLiterals = new Setlet<MapLiteralUse>();
     }
     _mapLiterals.add(mapLiteralUse);
   }
 
   @override
   Iterable<MapLiteralUse> get mapLiterals {
@@ skipping 379 matching lines @@
   @override
   void registerInstantiatedType(InterfaceType type) {
     registry.registerInstantiation(type);
   }
 
   @override
   DartType resolveTypeFromString(Node node, String typeName) {
     return visitor.resolveTypeFromString(node, typeName);
   }
 }