Create Namer and Emitter on codegen start.

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

 // Copyright (c) 2015, 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;
 
 class FrequencyBasedNamer extends Namer
     with _MinifiedFieldNamer, _MinifiedOneShotInterceptorNamer
     implements jsAst.TokenFinalizer {
   _FieldNamingRegistry fieldRegistry;
   List<TokenName> tokens = new List<TokenName>();
 
   Map<NamingScope, TokenScope> _tokenScopes =
       new Maplet<NamingScope, TokenScope>();
 
   // Some basic settings for smaller names
   String get isolateName => 'I';
   String get isolatePropertiesName => 'p';
   bool get shouldMinify => true;
 
   final String getterPrefix = 'g';
   final String setterPrefix = 's';
   final String callPrefix = ''; // this will create function names $<n>
 
   jsAst.Name get staticsPropertyName =>
       _staticsPropertyName ??= getFreshName(instanceScope, 'static');
 
-  FrequencyBasedNamer(Compiler compiler) : super(compiler) {
+  FrequencyBasedNamer(JavaScriptBackend backend, ClosedWorld closedWorld)
+      : super(backend, closedWorld) {
     fieldRegistry = new _FieldNamingRegistry(this);
   }
 
   TokenScope newScopeFor(NamingScope scope) {
     if (scope == instanceScope) {
       Set<String> illegalNames = new Set<String>.from(jsReserved);
       for (String illegal in MinifyNamer._reservedNativeProperties) {
         illegalNames.add(illegal);
         if (MinifyNamer._hasBannedPrefix(illegal)) {
           illegalNames.add(illegal.substring(1));
@@ skipping 92 matching lines @@
     String proposal;
     do {
       proposal = new String.fromCharCodes(_nextName);
       _incrementName();
     } while (MinifyNamer._hasBannedPrefix(proposal) ||
         illegalNames.contains(proposal));
 
     return proposal;
   }
 }