Move towards using WorldImpact for codegen

tests/compiler/dart2js/serialization/model_test_helper.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.
 
 library dart2js.serialization_model_test;
 
 import 'dart:async';
 import 'dart:io';
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
@@ skipping 55 matching lines @@
     bool verbose: false}) async {
   String testDescription = test != null ? test.name : '${entryPoint}';
   String id = index != null ? '$index: ' : '';
   String title = '${id}${testDescription}';
   Compiler compilerNormal = await measure(title, 'compile normal', () async {
     Compiler compilerNormal = compilerFor(
         memorySourceFiles: sourceFiles, options: [Flags.analyzeOnly]);
     compilerNormal.resolution.retainCachesForTesting = true;
     await compilerNormal.run(entryPoint);
     compilerNormal.phase = Compiler.PHASE_DONE_RESOLVING;
-    compilerNormal.openWorld.populate();
+    compilerNormal.openWorld.closeWorld();
     compilerNormal.backend.onResolutionComplete();
     compilerNormal.deferredLoadTask
         .onResolutionComplete(compilerNormal.mainFunction);
     return compilerNormal;
   });
 
   Compiler compilerDeserialized =
       await measure(title, 'compile deserialized', () async {
     Compiler compilerDeserialized = compilerFor(
         memorySourceFiles: sourceFiles,
         resolutionInputs: resolutionInputs,
         options: [Flags.analyzeOnly]);
     compilerDeserialized.resolution.retainCachesForTesting = true;
     await compilerDeserialized.run(entryPoint);
     compilerDeserialized.phase = Compiler.PHASE_DONE_RESOLVING;
-    compilerDeserialized.openWorld.populate();
+    compilerDeserialized.openWorld.closeWorld();
     compilerDeserialized.backend.onResolutionComplete();
     compilerDeserialized.deferredLoadTask
         .onResolutionComplete(compilerDeserialized.mainFunction);
     return compilerDeserialized;
   });
 
   return measure(title, 'check models', () async {
     checkAllImpacts(compilerNormal, compilerDeserialized, verbose: verbose);
 
     checkSets(
@@ skipping 288 matching lines @@
   check(outputUnit1, outputUnit2, 'OutputUnit.isMainOutput $message',
       outputUnit1.isMainOutput, outputUnit2.isMainOutput);
   checkSetEquivalence(
       outputUnit1,
       outputUnit2,
       'OutputUnit.imports $message',
       outputUnit1.imports,
       outputUnit2.imports,
       (a, b) => areElementsEquivalent(a.declaration, b.declaration));
 }