Roll Observatory packages and add a roll script

analyzer/lib/src/util/lru_map.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 engine.utilities.lru_cache;
-
-import 'dart:collection';
-
-/**
- * This handler is notified when an item is evicted from the cache.
- */
-typedef EvictionHandler<K, V>(K key, V value);
-
-/**
- * A hash-table based cache implementation.
- *
- * When it reaches the specified number of items, the item that has not been
- * accessed (both get and put) recently is evicted.
- */
-class LRUMap<K, V> {
-  final LinkedHashMap<K, V> _map = new LinkedHashMap<K, V>();
-  final int _maxSize;
-  final EvictionHandler _handler;
-
-  LRUMap(this._maxSize, [this._handler]);
-
-  /**
-   * Returns the value for the given [key] or null if [key] is not
-   * in the cache.
-   */
-  V get(K key) {
-    V value = _map.remove(key);
-    if (value != null) {
-      _map[key] = value;
-    }
-    return value;
-  }
-
-  /**
-   * Associates the [key] with the given [value].
-   *
-   * If the cache is full, an item that has not been accessed recently is
-   * evicted.
-   */
-  void put(K key, V value) {
-    _map.remove(key);
-    _map[key] = value;
-    if (_map.length > _maxSize) {
-      K evictedKey = _map.keys.first;
-      V evictedValue = _map.remove(evictedKey);
-      if (_handler != null) {
-        _handler(evictedKey, evictedValue);
-      }
-    }
-  }
-
-  /**
-   * Removes the association for the given [key].
-   */
-  void remove(K key) {
-    _map.remove(key);
-  }
-}