Remove `disableNewTaskModel` failsafe.

lib/src/driver.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.driver;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ skipping 213 matching lines @@
     }
     if (options.lints != _previousOptions.lints) {
       return false;
     }
     if (options.strongMode != _previousOptions.strongMode) {
       return false;
     }
     if (options.enableSuperMixins != _previousOptions.enableSuperMixins) {
       return false;
     }
-    if (options.disableNewTaskModel != _previousOptions.disableNewTaskModel) {
-      return false;
-    }
     return true;
   }
 
   /// Decide on the appropriate policy for which files need to be fully parsed
   /// and which files need to be diet parsed, based on [options], and return an
   /// [AnalyzeFunctionBodiesPredicate] that implements this policy.
   AnalyzeFunctionBodiesPredicate _chooseDietParsingPolicy(
       CommandLineOptions options) {
     if (_isBatch) {
       // As analyzer is currently implemented, once a file has been diet
@@ skipping 134 matching lines @@
     return new FileBasedSource(sourceFile, uri);
   }
 
   /// Create an analysis context that is prepared to analyze sources according
   /// to the given [options], and store it in [_context].
   void _createAnalysisContext(CommandLineOptions options) {
     if (_canContextBeReused(options)) {
       return;
     }
     _previousOptions = options;
-    // Determine whether the new task model should be used.
-    AnalysisEngine.instance.useTaskModel = !options.disableNewTaskModel;
     // Choose a package resolution policy and a diet parsing policy based on
     // the command-line options.
     SourceFactory sourceFactory = _chooseUriResolutionPolicy(options);
     AnalyzeFunctionBodiesPredicate dietParsingPolicy =
         _chooseDietParsingPolicy(options);
     // Create a context using these policies.
     AnalysisContext context = AnalysisEngine.instance.createAnalysisContext();
 
     context.sourceFactory = sourceFactory;
 
@@ skipping 234 matching lines @@
     for (var package in packages) {
       var packageName = path.basename(package.path);
       var realPath = package.resolveSymbolicLinksSync();
       result[packageName] = [
         PhysicalResourceProvider.INSTANCE.getFolder(realPath)
       ];
     }
     return result;
   }
 }