Fix an issue with restoring certain lint issues from summary files.

pkg/analyzer/lib/src/lint/registry.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.
 
 import 'dart:collection';
 
 import 'package:analyzer/src/lint/config.dart';
 import 'package:analyzer/src/lint/linter.dart';
 
 /**
@@ skipping 27 matching lines @@
    * Return a list of the rules that are defined.
    */
   Iterable<LintRule> get rules => _ruleMap.values;
 
   /**
    * Return the lint rule with the given [name].
    */
   LintRule operator [](String name) => _ruleMap[name];
 
   /**
+   * Return the lint rule with the given [name].
+   */
+  LintRule getRule(String name) => _ruleMap[name];
+
+  /**
    * Return a list of the lint rules explicitly enabled by the given [config].
    *
    * For example:
    *     my_rule: true
    *
    * enables `my_rule`.
    *
    * Unspecified rules are treated as disabled by default.
    */
   Iterable<LintRule> enabled(LintConfig config) => rules
       .where((rule) => config.ruleConfigs.any((rc) => rc.enables(rule.name)));
 
   /**
    * Add the given lint [rule] to this registry.
    */
   void register(LintRule rule) {
     _ruleMap[rule.name] = rule;
   }
 
   /**
    * Add the given lint [rule] to this registry and mark it as being a default
    * lint (one that will be run if lints are requested but no rules are enabled.
    */
   void registerDefault(LintRule rule) {
     register(rule);
     _defaultRules.add(rule);
   }
 }