Add minimal yaml support to the engine

pkg/analyzer/lib/src/plugin/engine_plugin.dart

Index: pkg/analyzer/lib/src/plugin/engine_plugin.dart
diff --git a/pkg/analyzer/lib/src/plugin/engine_plugin.dart b/pkg/analyzer/lib/src/plugin/engine_plugin.dart
index 07b0defbd2b37ab17b7950da4b47f2a2bb376a4e..c2ad5769580e93b6e306b347bdb4dfec2dac977b 100644
--- a/pkg/analyzer/lib/src/plugin/engine_plugin.dart
+++ b/pkg/analyzer/lib/src/plugin/engine_plugin.dart
@@ -14,6 +14,7 @@ import 'package:analyzer/src/task/general.dart';
 import 'package:analyzer/src/task/html.dart';
 import 'package:analyzer/src/task/html_work_manager.dart';
 import 'package:analyzer/src/task/options_work_manager.dart';
+import 'package:analyzer/src/task/yaml.dart';
 import 'package:analyzer/task/model.dart';
 import 'package:plugin/plugin.dart';
 
@@ -240,6 +241,10 @@ class EnginePlugin implements Plugin {
     registerExtension(taskId, DartScriptsTask.DESCRIPTOR);
     registerExtension(taskId, HtmlErrorsTask.DESCRIPTOR);
     registerExtension(taskId, ParseHtmlTask.DESCRIPTOR);
+    //
+    // Register YAML tasks.
+    //
+    registerExtension(taskId, ParseYamlTask.DESCRIPTOR);
   }
 
   void _registerWorkManagerFactoryExtensions(