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

pkg/compiler/lib/src/use_unused_api.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.
 
 /// This file use methods that aren't used by dart2js.dart, but that we wish to
 /// keep anyway. This might be general API that isn't currently in use,
 /// debugging aids, or API only used for testing (see TODO below).
 
 library dart2js.use_unused_api;
 
@@ skipping 282 matching lines @@
 useProgramBuilder(program_builder.ProgramBuilder builder) {
   builder.buildMethodHackForIncrementalCompilation(null);
   builder.buildFieldsHackForIncrementalCompilation(null);
 }
 
 useSemanticVisitor() {
   new semantic_visitor.BulkSendVisitor().apply(null, null);
   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);
-}