Allow null as a synonym for {} when decoding JSON objects.

pkg/analysis_server/test/domain_analysis_test.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 test.domain.analysis;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/constants.dart';
@@ skipping 123 matching lines @@
     group('updateOptions', () {
       test('invalid', () {
         var request = new Request('0', ANALYSIS_UPDATE_OPTIONS, {OPTIONS: {
           'not-an-option': true
         }});
         var response = handler.handleRequest(request);
         // Invalid options should be silently ignored.
         expect(response, isResponseSuccess('0'));
       });
 
+      test('null', () {
+        // null is allowed as a synonym for {}.
+        var request = new Request('0', ANALYSIS_UPDATE_OPTIONS, {OPTIONS: null});
+        var response = handler.handleRequest(request);
+        expect(response, isResponseSuccess('0'));
+      });
+
       // TODO(paulberry): disabled because analyzeAngular is currently not in the API.
 //      test('valid', () {
 //        engine.AnalysisOptions oldOptions = server.contextDirectoryManager.defaultOptions;
 //        bool analyzeAngular = !oldOptions.analyzeAngular;
 //        bool enableDeferredLoading = oldOptions.enableDeferredLoading;
 //        var newOptions = new AnalysisOptions(analyzeAngular: analyzeAngular,
 //            enableDeferredLoading: enableDeferredLoading, enableEnums: false);
 //        var request = new AnalysisUpdateOptionsParams(newOptions).toRequest('0');
 //        var response = handler.handleRequest(request);
 //        expect(response, isResponseSuccess('0'));
@@ skipping 447 matching lines @@
     return waitForServerOperationsPerformed(server);
   }
 
   static String _getCodeString(code) {
     if (code is List<String>) {
       code = code.join('\n');
     }
     return code as String;
   }
 }