Reapply "Move the linter core to the analyzer package"

pkg/analyzer/lib/src/lint/registry.dart

Index: pkg/analyzer/lib/src/lint/registry.dart
diff --git a/pkg/analyzer/lib/src/lint/registry.dart b/pkg/analyzer/lib/src/lint/registry.dart
new file mode 100644
index 0000000000000000000000000000000000000000..20ce0367efcde1c8de0713ed4fbab4a15ec2d616
--- /dev/null
+++ b/pkg/analyzer/lib/src/lint/registry.dart
@@ -0,0 +1,42 @@
+// 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';
+
+/**
+ * Registry of contributed lint rules.
+ */
+class Registry extends Object with IterableMixin<LintRule> {
+  /**
+   * The default registry to be used by clients.
+   */
+  static final Registry ruleRegistry = new Registry();
+
+  Map<String, LintRule> _ruleMap = <String, LintRule>{};
+
+  @override
+  Iterator<LintRule> get iterator => _ruleMap.values.iterator;
+
+  Iterable<LintRule> get rules => _ruleMap.values;
+
+  LintRule operator [](String key) => _ruleMap[key];
+
+  /// All 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)));
+
+  void register(LintRule rule) {
+    _ruleMap[rule.name] = rule;
+  }
+}