Add JS implementation of LinkedHashMap.

runtime/lib/collection_patch.dart

 // Copyright (c) 2013, 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.
 
 patch class HashMap<K, V> {
   final _HashMapTable<K, V> _hashTable = new _HashMapTable<K, V>();
 
   /* patch */ HashMap() {
     _hashTable._container = this;
   }
@@ skipping 171 matching lines @@
   }
 
   /* patch */ void retainWhere(bool test(E element)) {
     _filterWhere(test, false);
   }
 
   /* patch */ void clear() {
     _table._clear();
   }
 }
+
+class _LinkedHashMapTable<K, V> extends _LinkedHashTable<K> {
+  static const int _INITIAL_CAPACITY = 8;
+  static const int _VALUE_INDEX = 3;
+
+  int get _entrySize => 4;
+
+  _LinkedHashMapTable() : super(_INITIAL_CAPACITY);
+
+  V _value(int offset) => _table[offset + _VALUE_INDEX];
+  void _setValue(int offset, V value) { _table[offset + _VALUE_INDEX] = value; }
+
+  _copyEntry(List oldTable, int fromOffset, int toOffset) {
+    _table[toOffset + _VALUE_INDEX] = oldTable[fromOffset + _VALUE_INDEX];
+  }
+}
+
+/**
+ * A hash-based map that iterates keys and values in key insertion order.
+ */
+patch class LinkedHashMap<K, V> {
+  final _LinkedHashMapTable _hashTable;
+
+  /* patch */ LinkedHashMap() : _hashTable = new _LinkedHashMapTable<K, V>() {
+    _hashTable._container = this;
+  }
+
+  /* patch */ bool containsKey(K key) {
+    return _hashTable._get(key) >= 0;
+  }
+
+  /* patch */ bool containsValue(V value) {
+    int modificationCount = _hashTable._modificationCount;
+    for (int offset = _hashTable._next(_LinkedHashTable._HEAD_OFFSET);
+         offset != _LinkedHashTable._HEAD_OFFSET;
+         offset = _hashTable._next(offset)) {
+      if (_hashTable._value(offset) == value) {
+        return true;
+      }
+      // The == call may modify the table.
+      _hashTable._checkModification(modificationCount);
+    }
+    return false;
+  }
+
+  /* patch */ void addAll(Map<K, V> other) {
+    other.forEach((K key, V value) {
+      int offset = _hashTable._put(key);
+      _hashTable._setValue(offset, value);
+      _hashTable._checkCapacity();
+    });
+  }
+
+  /* patch */ V operator [](K key) {
+    int offset = _hashTable._get(key);
+    if (offset >= 0) return _hashTable._value(offset);
+    return null;
+  }
+
+  /* patch */ void operator []=(K key, V value) {
+    int offset = _hashTable._put(key);
+    _hashTable._setValue(offset, value);
+    _hashTable._checkCapacity();
+  }
+
+  /* patch */ V putIfAbsent(K key, V ifAbsent()) {
+    int offset = _hashTable._probeForAdd(_hashTable._hashCodeOf(key), key);
+    Object entry = _hashTable._table[offset];
+    if (!_hashTable._isFree(entry)) {
+      return _hashTable._value(offset);
+    }
+    int modificationCount = _hashTable._modificationCount;
+    V value = ifAbsent();
+    if (modificationCount == _hashTable._modificationCount) {
+      _hashTable._setKey(offset, key);
+      _hashTable._setValue(offset, value);
+      _hashTable._linkLast(offset);
+      if (entry == null) {
+        _hashTable._entryCount++;
+        _hashTable._checkCapacity();
+      } else {
+        assert(identical(entry, _TOMBSTONE));
+        _hashTable._deletedCount--;
+      }
+      _hashTable._recordModification();
+    } else {
+      // The table might have changed, so we can't trust [offset] any more.
+      // Do another lookup before setting the value.
+      offset = _hashTable._put(key);
+      _hashTable._setValue(offset, value);
+      _hashTable._checkCapacity();
+    }
+    return value;
+  }
+
+  /* patch */ V remove(K key) {
+    int offset = _hashTable._remove(key);
+    if (offset < 0) return null;
+    Object oldValue = _hashTable._value(offset);
+    _hashTable._setValue(offset, null);
+    _hashTable._checkCapacity();
+    return oldValue;
+  }
+
+  /* patch */ void clear() {
+    _hashTable._clear();
+  }
+
+  /* patch */ void forEach(void action (K key, V value)) {
+    int modificationCount = _hashTable._modificationCount;
+    for (int offset = _hashTable._next(_LinkedHashTable._HEAD_OFFSET);
+         offset != _LinkedHashTable._HEAD_OFFSET;
+         offset = _hashTable._next(offset)) {
+      action(_hashTable._key(offset), _hashTable._value(offset));
+      _hashTable._checkModification(modificationCount);
+    }
+  }
+
+  /* patch */ Iterable<K> get keys =>
+      new _LinkedHashTableKeyIterable<K>(_hashTable);
+
+  /* patch */ Iterable<V> get values =>
+      new _LinkedHashTableValueIterable<V>(_hashTable,
+                                           _LinkedHashMapTable._VALUE_INDEX);
+
+  /* patch */ int get length => _hashTable._elementCount;
+
+  /* patch */ bool get isEmpty => _hashTable._elementCount == 0;
+}