Extract ResolutionWorldBuilderBase from ElementResolutionWorldBuilder

pkg/compiler/lib/src/kernel/world_builder.dart

 // Copyright (c) 2017, 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.kernel.world_builder;
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../common.dart';
 import '../common/backend_api.dart';
@@ skipping 141 matching lines @@
     return member != null ? getConstructor(member) : null;
   }
 
   KClass _getClass(ir.Class node, [KClassEnv classEnv]) {
     return _classMap.putIfAbsent(node, () {
       KLibrary library = _getLibrary(node.enclosingLibrary);
       if (classEnv == null) {
         classEnv = _libraryEnvs[library.libraryIndex].lookupClass(node.name);
       }
       _classEnvs.add(classEnv);
-      return new KClass(library, _classMap.length, node.name);
+      return new KClass(library, _classMap.length, node.name,
+          isAbstract: node.isAbstract);
     });
   }
 
   KTypeVariable _getTypeVariable(ir.TypeParameter node) {
     return _typeVariableMap.putIfAbsent(node, () {
       if (node.parent is ir.Class) {
         ir.Class cls = node.parent;
         int index = cls.typeParameters.indexOf(node);
         return new KTypeVariable(_getClass(cls), node.name, index);
       }
@@ skipping 422 matching lines @@
     }
     return member;
   }
 
   @override
   ClassEntity getSuperClass(ClassEntity cls) {
     throw new UnimplementedError('KernelElementEnvironment.getSuperClass');
   }
 
   @override
+  void forEachSupertype(ClassEntity cls, void f(InterfaceType supertype)) {
+    throw new UnimplementedError('KernelElementEnvironment.forEachSupertype');
+  }
+
+  @override
   void forEachMixin(ClassEntity cls, void f(ClassEntity mixin)) {
     throw new UnimplementedError('KernelElementEnvironment.forEachMixin');
   }
 
   @override
   void forEachClassMember(
       ClassEntity cls, void f(ClassEntity declarer, MemberEntity member)) {
     throw new UnimplementedError(
         'KernelElementEnvironment.forEachInstanceMember');
   }
@@ skipping 271 matching lines @@
   }
 
   InterfaceType getMixinTypeForClass(KClass cls) {
     KClassEnv env = builder._classEnvs[cls.classIndex];
     ir.Supertype mixedInType = env.cls.mixedInType;
     if (mixedInType == null) return null;
     return builder.createInterfaceType(
         mixedInType.classNode, mixedInType.typeArguments);
   }
 }