Add AnalysisContext.onResultInvalidated(descriptor).

pkg/analyzer/lib/src/task/options_work_manager.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 analyzer.src.task.options_work_manager;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/context/cache.dart';
-import 'package:analyzer/src/generated/engine.dart'
-    show
-        AnalysisEngine,
-        AnalysisErrorInfo,
-        AnalysisErrorInfoImpl,
-        AnalysisOptions,
-        CacheState,
-        InternalAnalysisContext;
+import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/task/options.dart';
 import 'package:analyzer/task/model.dart';
 
 /// The manager for `.analysis_options` specific analysis.
 class OptionsWorkManager implements WorkManager {
   /// The context for which work is being managed.
   final InternalAnalysisContext context;
 
@@ skipping 134 matching lines @@
   }
 
   /// Returns `true` if the given [result] of the given [target] needs
   /// computing, i.e. it is not in the valid and not in the error state.
   bool _needsComputing(AnalysisTarget target, ResultDescriptor result) {
     CacheState state = analysisCache.getState(target, result);
     return state != CacheState.VALID && state != CacheState.ERROR;
   }
 
   /// Return `true` if the given target is an `.analysis_options` source.
-  static bool _isOptionsSource(AnalysisTarget target) => target is Source &&
+  static bool _isOptionsSource(AnalysisTarget target) =>
+      target is Source &&
       AnalysisEngine.isAnalysisOptionsFileName(target.fullName);
 }