Break up another large file

pkg/analyzer/lib/plugin/options.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.
 
 /// Support for client code that wants to consume options contributed to the
 /// analysis options file.
 library analyzer.plugin.options;
 
+import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/src/generated/engine.dart';
-import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/plugin/options_plugin.dart';
 import 'package:plugin/plugin.dart';
 import 'package:yaml/yaml.dart';
 
 /// The identifier of the extension point that allows plugins to access
 /// options defined in the analysis options file. The object used as an
 /// extension must be an [OptionsProcessor].
 final String OPTIONS_PROCESSOR_EXTENSION_POINT_ID = Plugin.join(
     OptionsPlugin.UNIQUE_IDENTIFIER,
     OptionsPlugin.OPTIONS_PROCESSOR_EXTENSION_POINT);
@@ skipping 54 matching lines @@
 /// Validates options as defined in an analysis options file.
 ///
 /// Clients may implement this class when implementing plugins.
 ///
 /// See [OptionsProcessor] for a description of the options file format.
 ///
 abstract class OptionsValidator {
   /// Validate [options], reporting any errors to the given [reporter].
   void validate(ErrorReporter reporter, Map<String, YamlNode> options);
 }