Use the unused [assembleCode].

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;
 
 import '../compiler.dart' as api;
 
 import 'colors.dart' as colors;
 import 'constants/values.dart' as constants;
 import 'cps_ir/cps_ir_builder.dart' as ir_builder;
 import 'cps_ir/cps_ir_nodes_sexpr.dart' as cps_ir_nodes_sexpr;
 import 'dart_types.dart' as dart_types;
 import 'dart2js.dart' as dart2js;
 import 'dart2jslib.dart' as dart2jslib;
 import 'elements/elements.dart' as elements;
 import 'elements/modelx.dart' as modelx;
 import 'elements/visitor.dart' as elements_visitor;
 import 'filenames.dart' as filenames;
 import 'inferrer/concrete_types_inferrer.dart' as concrete_types_inferrer;
 import 'inferrer/type_graph_inferrer.dart' as type_graph_inferrer;
 import 'io/code_output.dart' as io;
 import 'js/js.dart' as js;
+import 'js_backend/js_backend.dart' as js_backend;
 import 'js_emitter/js_emitter.dart' as js_emitter;
 import 'source_file_provider.dart' as source_file_provider;
 import 'ssa/ssa.dart' as ssa;
 import 'tree/tree.dart' as tree;
 import 'universe/universe.dart' as universe;
 import 'util/util.dart' as util;
 
 import 'scanner/scannerlib.dart' show
     PartialClassElement,
     PartialFunctionElement;
 
 class ElementVisitor extends elements_visitor.ElementVisitor {
   visitElement(e) {}
 }
 
 void main(List<String> arguments) {
   useApi();
   dart2js.main(arguments);
   useConstant(null, null);
   useNode(null);
   useUtil(null);
   useSetlet(null);
   useImmutableEmptySet(null);
   useElementVisitor(new ElementVisitor());
   useJs(new js.Program(null));
   useJs(new js.Blob(null));
   useJs(new js.NamedFunction(null, null));
   useJs(new js.ArrayHole());
+  useJsBackend(null);
   useConcreteTypesInferrer(null);
   useColor();
   useFilenames();
   useSsa(null);
   useCodeBuffer(null);
   usedByTests();
   useElements(null, null, null, null, null);
   useIr(null, null, null);
   useCompiler(null);
   useTypes();
@@ skipping 97 matching lines @@
     ..visitTypeVariableElement(null)
     ..visitTypedefElement(null)
     ..visitVariableElement(null)
     ..visitWarnOnUseElement(null);
 }
 
 useJs(js.Node node) {
   node.asVariableUse();
 }
 
+useJsBackend(js_backend.JavaScriptBackend backend) {
+  backend.assembleCode(null);
+}
+
 useConcreteTypesInferrer(concrete_types_inferrer.ConcreteTypesInferrer c) {
   c.debug();
 }
 
 useColor() {
   colors.white(null);
   colors.blue(null);
   colors.yellow(null);
   colors.black(null);
 }
@@ skipping 84 matching lines @@
   new dart_types.ResolvedTypedefType(null, null, null).unalias(null);
 }
 
 useCodeEmitterTask(js_emitter.CodeEmitterTask codeEmitterTask) {
   codeEmitterTask.oldEmitter.clearCspPrecompiledNodes();
 }
 
 useScript(dart2jslib.Script script) {
   script.copyWithFile(null);
 }