Convert EnginePlugin.taskDescriptors into a getter.

pkg/analyzer/lib/src/plugin/engine_plugin.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.src.plugin.engine_plugin;
 
 import 'package:analyzer/plugin/plugin.dart';
 import 'package:analyzer/plugin/task.dart';
 import 'package:analyzer/src/task/dart.dart';
 import 'package:analyzer/src/task/general.dart';
@@ skipping 19 matching lines @@
    * The extension point that allows plugins to register new analysis tasks with
    * the analysis engine.
    */
   ExtensionPoint taskExtensionPoint;
 
   /**
    * Initialize a newly created plugin.
    */
   EnginePlugin();
 
+  /**
+   * Return a list containing all of the task descriptors that were contributed.
+   */
+  List<TaskDescriptor> get taskDescriptors => taskExtensionPoint.extensions;
+
   @override
   String get uniqueIdentifier => UNIQUE_IDENTIFIER;
 
   @override
   void registerExtensionPoints(RegisterExtensionPoint registerExtensionPoint) {
     taskExtensionPoint =
         registerExtensionPoint(TASK_EXTENSION_POINT, _validateTaskExtension);
   }
 
   @override
@@ skipping 26 matching lines @@
     registerExtension(taskId, ResolveUnitTypeNamesTask.DESCRIPTOR);
     registerExtension(taskId, ResolveVariableReferencesTask.DESCRIPTOR);
     registerExtension(taskId, ScanDartTask.DESCRIPTOR);
     registerExtension(taskId, VerifyUnitTask.DESCRIPTOR);
     //
     // Register HTML tasks.
     //
   }
 
   /**
-   * Return a list containing all of the task descriptors that were contributed.
-   */
-  List<TaskDescriptor> taskDescriptors() {
-    return taskExtensionPoint.extensions;
-  }
-
-  /**
    * Validate the given extension by throwing an [ExtensionError] if it is not a
    * valid domain.
    */
   void _validateTaskExtension(Object extension) {
     if (extension is! TaskDescriptor) {
       String id = taskExtensionPoint.uniqueIdentifier;
       throw new ExtensionError('Extensions to $id must be a TaskDescriptor');
     }
   }
 }