dart2js cps: Remove dart2dart from cps pipeline and clean up.

pkg/compiler/lib/src/cps_ir/optimizers.dart

Index: pkg/compiler/lib/src/cps_ir/optimizers.dart
diff --git a/pkg/compiler/lib/src/cps_ir/optimizers.dart b/pkg/compiler/lib/src/cps_ir/optimizers.dart
index 8fd3f50aa31fd33d1d572c2d5d5d98bf6e701a69..f1007c612cae0b60aeb8438ecc9502f99626d993 100644
--- a/pkg/compiler/lib/src/cps_ir/optimizers.dart
+++ b/pkg/compiler/lib/src/cps_ir/optimizers.dart
@@ -8,15 +8,13 @@ import 'cps_ir_nodes.dart';
 
 export 'type_propagation.dart' show TypePropagator, TypeSystem,
                                     UnitTypeSystem, TypeMaskSystem;
-
-part 'redundant_phi.dart';
-part 'shrinking_reductions.dart';
-
+export 'redundant_phi.dart' show RedundantPhiEliminator;
+export 'shrinking_reductions.dart' show ShrinkingReducer, ParentVisitor;
 
 /// An optimization pass over the CPS IR.
 abstract class Pass {
   /// Applies optimizations to root, rewriting it in the process.
-  void rewrite(RootNode root);
+  void rewrite(FunctionDefinition root);
 
   String get passName;
 }