Remove `disableNewTaskModel` failsafe.

lib/src/options.dart

 // Copyright (c) 2015, 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 analyzer_cli.src.options;
 
 import 'dart:io';
 
 import 'package:analyzer_cli/src/driver.dart';
 import 'package:args/args.dart';
@@ skipping 21 matching lines @@
 class CommandLineOptions {
   /// The path to an analysis options file
   final String analysisOptionsFile;
 
   /// The path to the dart SDK
   String dartSdkPath;
 
   /// A table mapping the names of defined variables to their values.
   final Map<String, String> definedVariables;
 
-  /// Whether to disable the new task model.
-  final bool disableNewTaskModel;
-
   /// Whether to report hints
   final bool disableHints;
 
   /// Whether to display version information
   final bool displayVersion;
 
   /// Whether to enable null-aware operators (DEP 9).
   final bool enableNullAwareOperators;
 
   /// Whether to strictly follow the specification when generating warnings on
@@ skipping 46 matching lines @@
   /// Whether to use strong static checking.
   final bool strongMode;
 
   /// Initialize options from the given parsed [args].
   CommandLineOptions._fromArgs(
       ArgResults args, Map<String, String> definedVariables)
       : dartSdkPath = args['dart-sdk'],
         this.definedVariables = definedVariables,
         analysisOptionsFile = args['options'],
         disableHints = args['no-hints'],
-        disableNewTaskModel = args['disable-new-task-model'],
         displayVersion = args['version'],
         enableNullAwareOperators = args['enable-null-aware-operators'],
         enableStrictCallChecks = args['enable-strict-call-checks'],
         enableSuperMixins = args['supermixin'],
         enableTypeChecks = args['enable_type_checks'],
         hintsAreFatal = args['fatal-hints'],
         ignoreUnrecognizedFlags = args['ignore-unrecognized-flags'],
         lints = args['lints'],
         log = args['log'],
         machineFormat = args['machine'] || args['format'] == 'machine',
@@ skipping 131 matching lines @@
           negatable: false)
       ..addOption('url-mapping',
           help: '--url-mapping=libraryUri,/path/to/library.dart directs the '
               'analyzer to use "library.dart" as the source for an import '
               'of "libraryUri".',
           allowMultiple: true,
           splitCommas: false)
       //
       // Hidden flags.
       //
-      ..addFlag('disable-new-task-model',
-          help: 'Disable the use of the new task model.',
-          defaultsTo: false,
-          negatable: false,
-          hide: true)
       ..addFlag('enable-async',
           help: 'Enable support for the proposed async feature.',
           defaultsTo: false,
           negatable: false,
           hide: true)
       ..addFlag('enable-enum',
           help: 'Enable support for the proposed enum feature.',
           defaultsTo: false,
           negatable: false,
           hide: true)
@@ skipping 207 matching lines @@
 
   int _getNextFlagIndex(args, i) {
     for (; i < args.length; ++i) {
       if (args[i].startsWith('--')) {
         return i;
       }
     }
     return i;
   }
 }