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

pkg/analysis_server/lib/src/get_handler.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.src.get_handler;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
@@ skipping 989 matching lines @@
           CONTEXT_QUERY_PARAM: folder.path
         }, key, _hasException(folderMap[folder])));
       });
       buffer.write('</p>');
 
       buffer.write('<p><b>Options</b></p>');
       buffer.write('<p>');
       _writeOption(
           buffer, 'Analyze functon bodies', options.analyzeFunctionBodies);
       _writeOption(buffer, 'Cache size', options.cacheSize);
+      _writeOption(buffer, 'Enable null-aware operators',
+          options.enableNullAwareOperators);
       _writeOption(
           buffer, 'Enable strict call checks', options.enableStrictCallChecks);
       _writeOption(buffer, 'Generate hints', options.hint);
       _writeOption(buffer, 'Generate dart2js hints', options.dart2jsHint);
       _writeOption(buffer, 'Generate errors in implicit files',
           options.generateImplicitErrors);
       _writeOption(
           buffer, 'Generate errors in SDK files', options.generateSdkErrors);
       _writeOption(buffer, 'Incremental resolution', options.incremental);
       _writeOption(buffer, 'Incremental resolution with API changes',
@@ skipping 558 matching lines @@
    */
   static String makeLink(
       String path, Map<String, String> params, String innerHtml,
       [bool hasError = false]) {
     Uri uri = new Uri(path: path, queryParameters: params);
     String href = HTML_ESCAPE.convert(uri.toString());
     String classAttribute = hasError ? ' class="error"' : '';
     return '<a href="$href"$classAttribute>$innerHtml</a>';
   }
 }