support `@virtual` fields, fix #27384

pkg/analyzer/lib/src/dart/element/handle.dart

 // Copyright (c) 2014, 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 analyzer.src.generated.element_handle;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/constant/value.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
@@ skipping 567 matching lines @@
   @override
   FieldElement get actualElement => super.actualElement as FieldElement;
 
   @override
   ClassElement get enclosingElement => actualElement.enclosingElement;
 
   @override
   bool get isEnumConstant => actualElement.isEnumConstant;
 
   @override
+  bool get isVirtual => actualElement.isVirtual;
+
+  @override
   ElementKind get kind => ElementKind.FIELD;
 
   @override
   VariableDeclaration computeNode() => actualElement.computeNode();
 }
 
 /**
  * A handle to a [FunctionElement].
  */
 class FunctionElementHandle extends ExecutableElementHandle
@@ skipping 514 matching lines @@
 
   @override
   bool get isStatic => actualElement.isStatic;
 
   @override
   DartType get type => actualElement.type;
 
   @override
   DartObject computeConstantValue() => actualElement.computeConstantValue();
 }