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

tests/compiler/dart2js/dictionary_types_test.dart

Index: tests/compiler/dart2js/dictionary_types_test.dart
diff --git a/tests/compiler/dart2js/dictionary_types_test.dart b/tests/compiler/dart2js/dictionary_types_test.dart
index afe9db55249c446174ffa374db61b68ac60c85bc..10edb5c0e4e099f5c05b31e24fc19d764b745526 100644
--- a/tests/compiler/dart2js/dictionary_types_test.dart
+++ b/tests/compiler/dart2js/dictionary_types_test.dart
@@ -112,7 +112,7 @@ void main() {
     });
     await compileAndTest("Union.dart", (types, getType, compiler) {
       Expect.equals(getType('nullOrInt'), types.uint31Type.nullable());
-      Expect.isTrue(getType('aString').containsOnlyString(compiler.world));
+      Expect.isTrue(getType('aString').containsOnlyString(compiler.closedWorld));
       Expect.equals(getType('doubleOrNull'), types.doubleType.nullable());
     });
     await compileAndTest("ValueType.dart", (types, getType, compiler) {