Remove direct access to enqueuer through use of WorldImpact

pkg/compiler/lib/src/common/codegen.dart

Index: pkg/compiler/lib/src/common/codegen.dart
diff --git a/pkg/compiler/lib/src/common/codegen.dart b/pkg/compiler/lib/src/common/codegen.dart
index 285e03290c1f6d4fe1a093ce99d2fa14bedc81a7..2a81a2c785fb885cc33cf9d7c8e11036a8c40c66 100644
--- a/pkg/compiler/lib/src/common/codegen.dart
+++ b/pkg/compiler/lib/src/common/codegen.dart
@@ -159,6 +159,11 @@ class CodegenRegistry {
 
   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);