Create Namer and Emitter on codegen start.

pkg/compiler/lib/src/compiler.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.
 
 library dart2js.compiler_base;
 
 import 'dart:async' show EventSink, Future;
 
 import '../compiler_new.dart' as api;
 import 'cache_strategy.dart' show CacheStrategy;
@@ skipping 702 matching lines @@
         globalInference.runGlobalTypeInference(
             mainFunction, closedWorld, closedWorldRefiner);
 
         if (stopAfterTypeInference) return;
 
         backend.onTypeInferenceComplete();
 
         reporter.log('Compiling...');
         phase = PHASE_COMPILING;
 
-        enqueuer.codegen.applyImpact(backend.onCodegenStart());
+        enqueuer.codegen.applyImpact(backend.onCodegenStart(closedWorld));
         if (compileAll) {
           libraryLoader.libraries.forEach((LibraryElement library) {
             enqueuer.codegen.applyImpact(computeImpactForLibrary(library));
           });
         }
         processQueue(enqueuer.codegen, mainFunction,
             onProgress: showCodegenProgress);
         enqueuer.codegen.logSummary(reporter.log);
 
-        int programSize = backend.assembleProgram();
+        int programSize = backend.assembleProgram(closedWorld);
 
         if (options.dumpInfo) {
           dumpInfoTask.reportSize(programSize);
           dumpInfoTask.dumpInfo(closedWorld);
         }
 
         backend.sourceInformationStrategy.onComplete();
 
         checkQueues();
       });
@@ skipping 1485 matching lines @@
   _ElementScanner(this.scanner);
   void scanLibrary(LibraryElement library) => scanner.scanLibrary(library);
   void scanUnit(CompilationUnitElement unit) => scanner.scan(unit);
 }
 
 class _EmptyEnvironment implements Environment {
   const _EmptyEnvironment();
 
   String valueOf(String key) => null;
 }