Add an analysis server option to enable null-aware-operator support.

pkg/analysis_server/lib/src/analysis_server.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.
 
 library analysis.server;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:math' show max;
 
@@ skipping 48 matching lines @@
 
 /**
  * Instances of the class [AnalysisServer] implement a server that listens on a
  * [CommunicationChannel] for analysis requests and process them.
  */
 class AnalysisServer {
   /**
    * The version of the analysis server. The value should be replaced
    * automatically during the build.
    */
-  static final String VERSION = '1.5.0';
+  static final String VERSION = '1.6.0';
 
   /**
    * The number of milliseconds to perform operations before inserting
    * a 1 millisecond delay so that the VM and dart:io can deliver content
    * to stdin. This should be removed once the underlying problem is fixed.
    */
   static int performOperationDelayFreqency = 25;
 
   /**
    * The channel from which requests are received and to which responses should
@@ skipping 1413 matching lines @@
   /**
    * The [PerformanceTag] for time spent in server request handlers.
    */
   static PerformanceTag serverRequests = new PerformanceTag('serverRequests');
 
   /**
    * The [PerformanceTag] for time spent in split store microtasks.
    */
   static PerformanceTag splitStore = new PerformanceTag('splitStore');
 }