Fix a typo in the docs

pkg/analyzer_plugin/lib/plugin/plugin.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 'dart:async';
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/physical_file_system.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart'
     show AnalysisDriverGeneric, AnalysisDriverScheduler;
@@ skipping 437 matching lines @@
 
   /**
    * The method that is called when an error has occurred in the analysis
    * server. This method will not be invoked under normal conditions.
    */
   void onError(Object exception, StackTrace stackTrace) {}
 
   /**
    * Send notifications corresponding to the given description of subscriptions.
    * The map is keyed by the path of each file for which notifications should be
-   * send and has values representing the list of services associated with the
+   * sent and has values representing the list of services associated with the
    * notifications to send.
    */
   void sendNotificationsForSubscriptions(
       Map<String, List<AnalysisService>> subscriptions);
 
   /**
    * Start this plugin by listening to the given communication [channel].
    */
   void start(PluginCommunicationChannel channel) {
     _channel = channel;
@@ skipping 113 matching lines @@
       response = new Response(id, requestTime,
           error: new RequestError(
               RequestErrorCode.PLUGIN_ERROR, exception.toString(),
               stackTrace: stackTrace.toString()));
     }
     if (response != null) {
       _channel.sendResponse(response);
     }
   }
 }