Remove the options plugin

pkg/analyzer/lib/src/plugin/options_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.options_plugin;
-
-import 'package:analyzer/plugin/options.dart';
-import 'package:analyzer/plugin/task.dart';
-import 'package:analyzer/src/task/options.dart';
-import 'package:plugin/plugin.dart';
-
-/// A plugin that defines the extension points and extensions that are defined
-/// by applications that want to consume options defined in the analysis
-/// options file.
-class OptionsPlugin implements Plugin {
-  /// The simple identifier of the extension point that allows plugins to
-  /// register new options validators.
-  static const String OPTIONS_VALIDATOR_EXTENSION_POINT = 'optionsValidator';
-
-  /// The unique identifier of this plugin.
-  static const String UNIQUE_IDENTIFIER = 'options.core';
-
-  /// The extension point that allows plugins to register new options
-  /// validators.
-  ExtensionPoint<OptionsValidator> optionsValidatorExtensionPoint;
-
-  /// All contributed options validators.
-  List<OptionsValidator> get optionsValidators =>
-      optionsValidatorExtensionPoint?.extensions ?? const <OptionsValidator>[];
-
-  @override
-  String get uniqueIdentifier => UNIQUE_IDENTIFIER;
-
-  @override
-  void registerExtensionPoints(RegisterExtensionPoint registerExtensionPoint) {
-    optionsValidatorExtensionPoint = new ExtensionPoint<OptionsValidator>(
-        this, OPTIONS_VALIDATOR_EXTENSION_POINT, null);
-    registerExtensionPoint(optionsValidatorExtensionPoint);
-  }
-
-  @override
-  void registerExtensions(RegisterExtension registerExtension) {
-    // Analyze options files.
-    registerExtension(
-        TASK_EXTENSION_POINT_ID, GenerateOptionsErrorsTask.DESCRIPTOR);
-    // Validate analyzer analysis options.
-    registerExtension(
-        OPTIONS_VALIDATOR_EXTENSION_POINT_ID, new AnalyzerOptionsValidator());
-  }
-}