Add support to pass the location of the analysis options file to plugins

pkg/analysis_server/lib/src/plugin/plugin_manager.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 'dart:collection';
 import 'dart:io' show Platform;
 
 import 'package:analysis_server/src/plugin/notification_manager.dart';
 import 'package:analyzer/context/context_root.dart' as analyzer;
@@ skipping 204 matching lines @@
    */
   ServerCommunicationChannel _createChannel();
 
   /**
    * Update the context roots that the plugin should be analyzing.
    */
   void _updatePluginRoots() {
     if (currentSession != null) {
       AnalysisSetContextRootsParams params = new AnalysisSetContextRootsParams(
           contextRoots
-              .map((analyzer.ContextRoot contextRoot) =>
-                  new ContextRoot(contextRoot.root, contextRoot.exclude))
+              .map((analyzer.ContextRoot contextRoot) => new ContextRoot(
+                  contextRoot.root, contextRoot.exclude,
+                  optionsFile: contextRoot.optionsFilePath))
               .toList());
       currentSession.sendRequest(params);
     }
   }
 }
 
 /**
  * An object used to manage the currently running plugins.
  */
 class PluginManager {
@@ skipping 642 matching lines @@
    * The completer that will be used to complete the future when the response is
    * received from the plugin.
    */
   final Completer<Response> completer;
 
   /**
    * Initialize a pending request.
    */
   _PendingRequest(this.method, this.requestTime, this.completer);
 }