Introducing a lint server plugin.

pkg/analysis_server/lib/src/plugin/linter_plugin.dart

Index: pkg/analysis_server/lib/src/plugin/linter_plugin.dart
diff --git a/pkg/analysis_server/lib/src/plugin/linter_plugin.dart b/pkg/analysis_server/lib/src/plugin/linter_plugin.dart
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+++ b/pkg/analysis_server/lib/src/plugin/linter_plugin.dart
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+// 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 analysis_server.src.plugin.linter_plugin;
+
+import 'package:analysis_server/src/services/linter/linter.dart';
+import 'package:analyzer/plugin/options.dart';
+import 'package:plugin/plugin.dart';
+
+/// The shared linter server plugin instance.
+final LinterServerPlugin linterServerPlugin = new LinterServerPlugin();
+
+/// A plugin that defines the extension points and extensions that enhance
+/// linting in the server.
+class LinterServerPlugin implements Plugin {
+  /// The unique identifier of this plugin.
+  static const String UNIQUE_IDENTIFIER = 'linter.server';
+
+  @override
+  String get uniqueIdentifier => UNIQUE_IDENTIFIER;
+
+  @override
+  void registerExtensionPoints(RegisterExtensionPoint registerExtensionPoint) {
+    // None.
+  }
+
+  @override
+  void registerExtensions(RegisterExtension registerExtension) {
+    //
+    // Register options validators.
+    //
+    registerExtension(
+        OPTIONS_VALIDATOR_EXTENSION_POINT_ID, new LinterRuleOptionsValidator());
+  }
+}