Split World usage into open, inference, and closed world.

tests/compiler/dart2js/compiler_helper.dart

Index: tests/compiler/dart2js/compiler_helper.dart
diff --git a/tests/compiler/dart2js/compiler_helper.dart b/tests/compiler/dart2js/compiler_helper.dart
index 7c7746389885381aacbbd4ed3e6da7c44426f7b4..146ba17147f8833e997e5ed64f3d57f2f94d1319 100644
--- a/tests/compiler/dart2js/compiler_helper.dart
+++ b/tests/compiler/dart2js/compiler_helper.dart
@@ -80,7 +80,7 @@ Future<String> compile(String code,
     compiler.backend.enqueueHelpers(compiler.enqueuer.resolution,
                                     compiler.globalDependencies);
     compiler.processQueue(compiler.enqueuer.resolution, element);
-    compiler.world.populate();
+    compiler.openWorld.populate();
     compiler.backend.onResolutionComplete();
     ResolutionWorkItem resolutionWork = new ResolutionWorkItem(element);
     resolutionWork.run(compiler, compiler.enqueuer.resolution);
@@ -215,17 +215,17 @@ types.TypeMask findTypeMask(compiler, String name,
   Expect.isNotNull(element, 'Could not locate $name');
   switch (how) {
     case 'exact':
-      return new types.TypeMask.exact(element, compiler.world);
+      return new types.TypeMask.exact(element, compiler.closedWorld);
     case 'nonNullExact':
-      return new types.TypeMask.nonNullExact(element, compiler.world);
+      return new types.TypeMask.nonNullExact(element, compiler.closedWorld);
     case 'subclass':
-      return new types.TypeMask.subclass(element, compiler.world);
+      return new types.TypeMask.subclass(element, compiler.closedWorld);
     case 'nonNullSubclass':
-      return new types.TypeMask.nonNullSubclass(element, compiler.world);
+      return new types.TypeMask.nonNullSubclass(element, compiler.closedWorld);
     case 'subtype':
-      return new types.TypeMask.subtype(element, compiler.world);
+      return new types.TypeMask.subtype(element, compiler.closedWorld);
     case 'nonNullSubtype':
-      return new types.TypeMask.nonNullSubtype(element, compiler.world);
+      return new types.TypeMask.nonNullSubtype(element, compiler.closedWorld);
   }
   Expect.fail('Unknown TypeMask constructor $how');
   return null;