Add CoreClasses

pkg/compiler/lib/src/js_backend/lookup_map_analysis.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.
 
 /// Analysis to determine how to generate code for `LookupMap`s.
 library compiler.src.js_backend.lookup_map_analysis;
 
 import '../common.dart';
 import '../common/registry.dart' show Registry;
 import '../compiler.dart' show Compiler;
@@ skipping 187 matching lines @@
     assert(isLookupMap(lookupMap));
     _lookupMaps.putIfAbsent(lookupMap,
         () => new _LookupMapInfo(lookupMap, this).._updateUsed());
   }
 
   /// Whether [key] is a constant value whose type overrides equals.
   bool _overridesEquals(ConstantValue key) {
     if (key is ConstructedConstantValue) {
       ClassElement element = key.type.element;
       return _typesWithEquals.putIfAbsent(element, () =>
-          element.lookupMember('==').enclosingClass !=
-          backend.compiler.objectClass);
+          !element.lookupMember('==').enclosingClass.isObject);
     }
     return false;
   }
 
   /// Whether we need to preserve [key]. This is true for keys that are not
   /// candidates for tree-shaking in the first place (primitives and non-type
   /// const values overriding equals) and keys that we have seen in the program.
   bool _shouldKeep(ConstantValue key) =>
       key.isPrimitive || _inUse.contains(key) || _overridesEquals(key);
 
@@ skipping 213 matching lines @@
       }
     } else {
       original.fields[analysis.entriesField] =
           new ListConstantValue(listType, keyValuePairs);
     }
   }
 }
 
 final _validLookupMapVersionConstraint =
     new VersionConstraint.parse('^0.0.1');