Cherry-pick r44373, r44378, and r44275.

pkg/analysis_server/lib/src/operation/operation_queue.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 operation.queue;
 
 import 'dart:collection';
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/operation/operation.dart';
+import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 /**
  * A queue of operations in an [AnalysisServer].
  */
 class ServerOperationQueue {
   final List<Queue<ServerOperation>> _queues = <Queue<ServerOperation>>[];
 
   ServerOperationQueue() {
     for (int i = 0; i < ServerOperationPriority.COUNT; i++) {
@@ skipping 23 matching lines @@
   /**
    * Removes all elements in the queue.
    */
   void clear() {
     for (Queue<ServerOperation> queue in _queues) {
       queue.clear();
     }
   }
 
   /**
+   * The given [context] has been removed, so all pending operations that refer
+   * to it should be removed from the queue.
+   */
+  void contextRemoved(AnalysisContext context) {
+    for (Queue<ServerOperation> queue in _queues) {
+      queue.removeWhere((operation) => operation.context == context);
+    }
+  }
+
+  /**
    * Return the next operation to perform, or `null` if the queue is empty.
    * This method does not change the queue.
    */
   ServerOperation peek() {
     for (Queue<ServerOperation> queue in _queues) {
       if (!queue.isEmpty) {
         return queue.first;
       }
     }
     return null;
@@ skipping 47 matching lines @@
       for (var operation in queue) {
         if (test(operation)) {
           queue.remove(operation);
           return operation;
         }
       }
     }
     return null;
   }
 }