Make Stream abstract as it is in the actual SDK.

pkg/analyzer/test/generated/non_error_resolver_driver_test.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.
 
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'non_error_resolver_test.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(NonErrorResolverTest_Driver);
   });
 }
 
 @reflectiveTest
 class NonErrorResolverTest_Driver extends NonErrorResolverTest {
   @override
   bool get enableNewAnalysisDriver => true;
 
   @failingTest
   @override
   test_invalidAnnotation_constantVariable_field_importWithPrefix() {
     return super
         .test_invalidAnnotation_constantVariable_field_importWithPrefix();
   }
 
   @failingTest
   @override
-  test_issue_24191() {
-    return super.test_issue_24191();
-  }
-
-  @failingTest
-  @override
   test_nativeConstConstructor() {
     return super.test_nativeConstConstructor();
   }
 
   @failingTest
   @override
   test_nativeFunctionBodyInNonSDKCode_function() {
     return super.test_nativeFunctionBodyInNonSDKCode_function();
   }
 }