Change the type of Error.code from int to String.

pkg/analysis_server/test/integration/protocol_matchers.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".
 
 /**
  * Matchers for data types defined in the analysis server API
@@ skipping 1051 matching lines @@
   "TYPE_PARAMETER",
   "UNKNOWN",
   "UNIT_TEST_GROUP",
   "UNIT_TEST_TEST"
 ]);
 
 /**
  * Error
  *
  * {
- *   "code": int
+ *   "code": String
  *   "message": String
  *   "data": optional object
  * }
  */
 final Matcher isError = new MatchesJsonObject(
   "Error", {
-    "code": isInt,
+    "code": isString,
     "message": isString
   }, optionalFields: {
     "data": isObject
   });
 
 /**
  * ErrorFixes
  *
  * {
  *   "error": AnalysisError
@@ skipping 758 matching lines @@
  *
  * {
  *   "newName": String
  * }
  */
 final Matcher isRenameOptions = new MatchesJsonObject(
   "rename options", {
     "newName": isString
   });