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

pkg/compiler/lib/src/use_unused_api.dart

Index: pkg/compiler/lib/src/use_unused_api.dart
diff --git a/pkg/compiler/lib/src/use_unused_api.dart b/pkg/compiler/lib/src/use_unused_api.dart
index dd46337100783e70bc3c8ece0334029c79600347..f9ac7dc1f60703891a34d0d226f9533b2233ed9b 100644
--- a/pkg/compiler/lib/src/use_unused_api.dart
+++ b/pkg/compiler/lib/src/use_unused_api.dart
@@ -300,18 +300,3 @@ useSemanticVisitor() {
   new semantic_visitor.TraversalVisitor(null).apply(null, null);
   new semantic_visitor.BulkDeclarationVisitor().apply(null, null);
 }
-
-class DummyTreeVisitor extends tree_ir.RootVisitor
-                          with tree_ir.InitializerVisitor {
-  visitFunctionDefinition(tree_ir.FunctionDefinition node) {}
-  visitConstructorDefinition(tree_ir.ConstructorDefinition node) {}
-  visitFieldDefinition(tree_ir.FieldDefinition node) {}
-
-  visitFieldInitializer(tree_ir.FieldInitializer node) {}
-  visitSuperInitializer(tree_ir.SuperInitializer node) {}
-}
-
-useTreeVisitors() {
-  new DummyTreeVisitor().visitRootNode(null);
-  new DummyTreeVisitor().visitInitializer(null);
-}