Restore auto-processing of plugins

pkg/analyzer/lib/src/generated/engine.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 analyzer.src.generated.engine;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 806 matching lines @@
    * [processRequiredPlugins].
    */
   List<Plugin> get requiredPlugins => <Plugin>[enginePlugin];
 
   /**
    * Return the task manager used to manage the tasks used to analyze code.
    */
   TaskManager get taskManager {
     if (_taskManager == null) {
       if (enginePlugin.taskExtensionPoint == null) {
-        throw new IllegalStateException(
-            'The analysis engine plugin has not been registered');
+        processRequiredPlugins();
       }
       _taskManager = new TaskManager();
       _taskManager.addTaskDescriptors(enginePlugin.taskDescriptors);
       // TODO(brianwilkerson) Create a way to associate different results with
       // different file suffixes, then make this pluggable.
       _taskManager.addGeneralResult(DART_ERRORS);
     }
     return _taskManager;
   }
 
@@ skipping 12 matching lines @@
     return new AnalysisContextImpl();
   }
 
   /**
    * A utility method that clients can use to process all of the required
    * plugins. This method can only be used by clients that do not need to
    * process any other plugins.
    */
   void processRequiredPlugins() {
     ExtensionManager manager = new ExtensionManager();
-    manager.processPlugins(AnalysisEngine.instance.requiredPlugins);
+    manager.processPlugins(requiredPlugins);
   }
 
   /**
    * Return `true` if the given [fileName] is an analysis options file.
    */
   static bool isAnalysisOptionsFileName(String fileName,
       [pathos.Context context]) {
     if (fileName == null) {
       return false;
     }
@@ skipping 1525 matching lines @@
    * The data that was created from the source.
    */
   final E data;
 
   /**
    * Initialize a newly created holder to associate the given [data] with the
    * given [modificationTime].
    */
   TimestampedData(this.modificationTime, this.data);
 }