dart2js CPS: Small cleanup of the compilation pipeline.

pkg/compiler/lib/src/js_backend/codegen/unsugar.dart

Index: pkg/compiler/lib/src/js_backend/codegen/unsugar.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/unsugar.dart b/pkg/compiler/lib/src/js_backend/codegen/unsugar.dart
index 7c18b605c15cfebc26edeaf9204c40553d7a0552..3f68eed7bee66f6c2bdc18a92988536dd6563611 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/unsugar.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/unsugar.dart
@@ -2,7 +2,7 @@ library dart2js.unsugar_cps;
 
 import '../../cps_ir/cps_ir_nodes.dart';
 
-import '../../cps_ir/optimizers.dart' show ParentVisitor;
+import '../../cps_ir/optimizers.dart' show ParentVisitor, Pass;
 import '../../constants/values.dart';
 import '../../elements/elements.dart';
 import '../../io/source_information.dart';
@@ -35,7 +35,7 @@ class InterceptorEntity extends Entity {
 ///  - Add explicit receiver argument for methods that are called in interceptor
 ///    calling convention.
 ///  - Convert two-parameter exception handlers to one-parameter ones.
-class UnsugarVisitor extends RecursiveVisitor {
+class UnsugarVisitor extends RecursiveVisitor implements Pass {
   Glue _glue;
   ParentVisitor _parentVisitor = new ParentVisitor();
 
@@ -49,6 +49,8 @@ class UnsugarVisitor extends RecursiveVisitor {
 
   UnsugarVisitor(this._glue);
 
+  String get passName => 'Unsugaring';
+
   bool methodUsesReceiverArgument(FunctionElement function) {
     assert(_glue.isInterceptedMethod(function));
     ClassElement clazz = function.enclosingClass.declaration;