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

pkg/compiler/lib/src/js_backend/namer.dart

 // Copyright (c) 2011, 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 js_backend.namer;
 
 import 'dart:collection' show HashMap;
 
 import 'package:js_runtime/shared/embedded_names.dart' show JsGetName;
 
@@ skipping 835 matching lines @@
           element, () => asEntity.declaredEntity.name);
     }
 
     // If the name of the field might clash with another field,
     // use a mangled field name to avoid potential clashes.
     // Note that if the class extends a native class, that native class might
     // have fields with fixed backend names, so we assume the worst and always
     // mangle the field names of classes extending native classes.
     // Methods on such classes are stored on the interceptor, not the instance,
     // so only fields have the potential to clash with a native property name.
-    ClassWorld classWorld = compiler.world;
+    ClassWorld classWorld = compiler.closedWorld;
     if (classWorld.isUsedAsMixin(enclosingClass) ||
         _isShadowingSuperField(element) ||
         _isUserClassExtendingNative(enclosingClass)) {
       String proposeName() => '${enclosingClass.name}_${element.name}';
       return _disambiguateInternalMember(element, proposeName);
     }
 
     // No superclass uses the disambiguated name as a property name, so we can
     // use it for this field. This generates nicer field names since otherwise
     // the field name would have to be mangled.
@@ skipping 1233 matching lines @@
   void addSuggestion(String original, String suggestion) {
     assert(!_suggestedNames.containsKey(original));
     _suggestedNames[original] = suggestion;
   }
 
   bool hasSuggestion(String original) => _suggestedNames.containsKey(original);
   bool isSuggestion(String candidate) {
     return _suggestedNames.containsValue(candidate);
   }
 }