Remove direct access to enqueuer through use of WorldImpact

pkg/compiler/lib/src/common/codegen.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.common.codegen;
 
 import '../common.dart';
 import '../compiler.dart' show Compiler;
 import '../constants/values.dart' show ConstantValue;
 import '../dart_types.dart' show DartType, InterfaceType;
@@ skipping 141 matching lines @@
 
   CodegenRegistry(Compiler compiler, AstElement currentElement)
       : this.compiler = compiler,
         this.currentElement = currentElement,
         this.worldImpact = new _CodegenImpact();
 
   bool get isForResolution => false;
 
   String toString() => 'CodegenRegistry for $currentElement';
 
+  /// Add the uses in [impact] to the impact of this registry.
+  void addImpact(WorldImpact impact) {
+    worldImpact.addImpact(impact);
+  }
+
   @deprecated
   void registerInstantiatedClass(ClassElement element) {
     registerInstantiation(element.rawType);
   }
 
   void registerStaticUse(StaticUse staticUse) {
     worldImpact.registerStaticUse(staticUse);
   }
 
   void registerDynamicUse(DynamicUse dynamicUse) {
@@ skipping 64 matching lines @@
 
   WorldImpact run(Compiler compiler, Enqueuer world) {
     if (world.isProcessed(element)) return const WorldImpact();
 
     registry = new CodegenRegistry(compiler, element);
     return compiler.codegen(this, world);
   }
 
   String toString() => 'CodegenWorkItem(${resolvedAst.element})';
 }