Make findElementReferences' "id" result optional.

pkg/analysis_server/lib/src/generated_protocol.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.
 //
 // This file has been automatically generated.  Please do not edit it manually.
 // To regenerate the file, use the script
 // "pkg/analysis_server/spec/generate_files".
 
 part of protocol;
 /**
@@ skipping 2197 matching lines @@
     hash = _JenkinsSmiHash.combine(hash, offset.hashCode);
     hash = _JenkinsSmiHash.combine(hash, includePotential.hashCode);
     return _JenkinsSmiHash.finish(hash);
   }
 }
 
 /**
  * search.findElementReferences result
  *
  * {
- *   "id": SearchId
+ *   "id": optional SearchId
  *   "element": optional Element
  * }
  */
 class SearchFindElementReferencesResult implements HasToJson {
   /**
    * The identifier used to associate results with this search request.
+   *
+   * If no element was found at the given location, this field will be absent,
+   * and no results will be reported via the search.results notification.
    */
   String id;
 
   /**
    * The element referenced or defined at the given offset and whose references
    * will be returned in the search results.
    *
    * If no element was found at the given location, this field will be absent.
    */
   Element element;
 
-  SearchFindElementReferencesResult(this.id, {this.element});
+  SearchFindElementReferencesResult({this.id, this.element});
 
   factory SearchFindElementReferencesResult.fromJson(JsonDecoder jsonDecoder, String jsonPath, Object json) {
     if (json == null) {
       json = {};
     }
     if (json is Map) {
       String id;
       if (json.containsKey("id")) {
         id = jsonDecoder._decodeString(jsonPath + ".id", json["id"]);
-      } else {
-        throw jsonDecoder.missingKey(jsonPath, "id");
       }
       Element element;
       if (json.containsKey("element")) {
         element = new Element.fromJson(jsonDecoder, jsonPath + ".element", json["element"]);
       }
-      return new SearchFindElementReferencesResult(id, element: element);
+      return new SearchFindElementReferencesResult(id: id, element: element);
     } else {
       throw jsonDecoder.mismatch(jsonPath, "search.findElementReferences result");
     }
   }
 
   factory SearchFindElementReferencesResult.fromResponse(Response response) {
     return new SearchFindElementReferencesResult.fromJson(
         new ResponseDecoder(), "result", response._result);
   }
 
   Map<String, dynamic> toJson() {
     Map<String, dynamic> result = {};
-    result["id"] = id;
+    if (id != null) {
+      result["id"] = id;
+    }
     if (element != null) {
       result["element"] = element.toJson();
     }
     return result;
   }
 
   Response toResponse(String id) {
     return new Response(id, result: toJson());
   }
 
@@ skipping 7483 matching lines @@
     return false;
   }
 
   @override
   int get hashCode {
     int hash = 0;
     hash = _JenkinsSmiHash.combine(hash, newName.hashCode);
     return _JenkinsSmiHash.finish(hash);
   }
 }