Move towards using WorldImpact for codegen

tests/compiler/dart2js/serialization/model_test_helper.dart

Index: tests/compiler/dart2js/serialization/model_test_helper.dart
diff --git a/tests/compiler/dart2js/serialization/model_test_helper.dart b/tests/compiler/dart2js/serialization/model_test_helper.dart
index c97d1ea87990cdf6f1ab4ee8ae4eb072e1741f32..90cde97f25cdf9d679edf824a0715cd6e99a357f 100644
--- a/tests/compiler/dart2js/serialization/model_test_helper.dart
+++ b/tests/compiler/dart2js/serialization/model_test_helper.dart
@@ -73,7 +73,7 @@ Future checkModels(Uri entryPoint,
     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);
@@ -89,7 +89,7 @@ Future checkModels(Uri entryPoint,
     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);