Extract OrderedTypeSetBuilderBase from OrderedTypeSetBuilder

pkg/compiler/lib/src/resolution/class_hierarchy.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.
 
 library dart2js.resolution.class_hierarchy;
 
 import '../common.dart';
 import '../common/resolution.dart' show Resolution;
 import '../common_elements.dart' show CommonElements;
 import '../elements/resolution_types.dart';
@@ skipping 520 matching lines @@
    *   supertypes(C) = [S, I1, I2] ++ supertypes(S) ++ supertypes(I1)
    *                   ++ supertypes(I2),
    * where ++ stands for list concatenation.
    *
    * This order makes sure that if a class implements an interface twice with
    * different type arguments, the type used in the most specific class comes
    * first.
    */
   void calculateAllSupertypes(BaseClassElementX cls) {
     if (cls.allSupertypesAndSelf != null) return;
-    final ResolutionDartType supertype = cls.supertype;
+    final ResolutionInterfaceType supertype = cls.supertype;
     if (supertype != null) {
       cls.allSupertypesAndSelf = new OrderedTypeSetBuilder(cls,
               reporter: reporter, objectType: commonElements.objectType)
           .createOrderedTypeSet(supertype, cls.interfaces);
     } else {
       assert(cls == resolution.commonElements.objectClass);
       cls.allSupertypesAndSelf =
           new OrderedTypeSet.singleton(cls.computeType(resolution));
     }
   }
@@ skipping 92 matching lines @@
     Identifier selector = node.selector.asIdentifier();
     var e = prefixElement.lookupLocalMember(selector.source);
     if (e == null || !e.impliesType) {
       reporter.reportErrorMessage(node.selector,
           MessageKind.CANNOT_RESOLVE_TYPE, {'typeName': node.selector});
       return;
     }
     loadSupertype(e, node);
   }
 }