Remove the old task model

pkg/analysis_server/lib/src/domain_diagnostic.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 src.domain_diagnostic;
+library analysis_server.src.domain_diagnostic;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:core' hide Resource;
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/utilities/average.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/context/context.dart';
-import 'package:analyzer/src/generated/engine.dart'
-    hide AnalysisCache, AnalysisContextImpl;
+import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/utilities_collection.dart';
 import 'package:analyzer/src/task/driver.dart';
 import 'package:analyzer/task/model.dart';
 
 int _workItemCount(AnalysisContextImpl context) {
   AnalysisDriver driver = context.driver;
   List<WorkItem> items = driver.currentWorkOrder?.workItems;
   return items?.length ?? 0;
 }
@@ skipping 152 matching lines @@
             averages[folder] = average;
           }
           average.addSample(_workItemCount(context));
         }
       });
     } on Exception {
       stop();
     }
   }
 }