Add union types to the analysis server API spec.

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 192 matching lines @@
 
 /**
  * analysis.setSubscriptions result
  */
 final Matcher isAnalysisSetSubscriptionsResult = isNull;
 
 /**
  * analysis.updateContent params
  *
  * {
- *   "files": Map<FilePath, object>
+ *   "files": Map<FilePath, AddContentOverlay | ChangeContentOverlay | RemoveContentOverlay>
  * }
  */
 final Matcher isAnalysisUpdateContentParams = new MatchesJsonObject(
   "analysis.updateContent params", {
-    "files": isMapOf(isFilePath, isObject)
+    "files": isMapOf(isFilePath, isOneOf([isAddContentOverlay, isChangeContentOverlay, isRemoveContentOverlay]))
   });
 
 /**
  * analysis.updateContent result
  */
 final Matcher isAnalysisUpdateContentResult = isNull;
 
 /**
  * analysis.updateOptions params
  *
@@ skipping 1637 matching lines @@
  *
  * {
  *   "newName": String
  * }
  */
 final Matcher isRenameOptions = new MatchesJsonObject(
   "rename options", {
     "newName": isString
   });