Create Namer and Emitter on codegen start.

pkg/compiler/lib/src/js_backend/minify_namer.dart

 // Copyright (c) 2011, 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.
 
 part of js_backend.namer;
 
 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  */
 class MinifyNamer extends Namer
     with
         _MinifiedFieldNamer,
         _MinifyConstructorBodyNamer,
         _MinifiedOneShotInterceptorNamer {
-  MinifyNamer(Compiler compiler) : super(compiler) {
+  MinifyNamer(JavaScriptBackend backend, ClosedWorld closedWorld)
+      : super(backend, closedWorld) {
     reserveBackendNames();
     fieldRegistry = new _FieldNamingRegistry(this);
   }
 
   _FieldNamingRegistry fieldRegistry;
 
   String get isolateName => 'I';
   String get isolatePropertiesName => 'p';
   bool get shouldMinify => true;
 
@@ skipping 358 matching lines @@
     String prefix =
         selector.isGetter ? r"$get" : selector.isSetter ? r"$set" : "";
     String callSuffix = selector.isCall
         ? callSuffixForStructure(selector.callStructure).join()
         : "";
     String suffix = suffixForGetInterceptor(classes);
     String fullName = "\$intercepted$prefix\$$root$callSuffix\$$suffix";
     return _disambiguateInternalGlobal(fullName);
   }
 }