Revert "Use an ES6 map for a linked identity hash map."

sdk/lib/_internal/compiler/js_lib/collection_patch.dart

Index: sdk/lib/_internal/compiler/js_lib/collection_patch.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/collection_patch.dart b/sdk/lib/_internal/compiler/js_lib/collection_patch.dart
index dcef50665806042b1c54e63839a7d06188819d7a..9df7c993393011693306552cfbee61454f19a616 100644
--- a/sdk/lib/_internal/compiler/js_lib/collection_patch.dart
+++ b/sdk/lib/_internal/compiler/js_lib/collection_patch.dart
@@ -9,8 +9,6 @@ import 'dart:_js_helper' show
     JsLinkedHashMap, LinkedHashMapCell, LinkedHashMapKeyIterable,
     LinkedHashMapKeyIterator;
 
-const _USE_ES6_MAPS = const bool.fromEnvironment("dart2js.use.es6.maps");
-
 @patch
 class HashMap<K, V> {
   @patch
@@ -502,7 +500,7 @@ class LinkedHashMap<K, V> {
       } else {
         if (identical(identityHashCode, hashCode) &&
             identical(identical, equals)) {
-          return new _LinkedIdentityHashMap<K, V>.es6();
+          return new _LinkedIdentityHashMap<K, V>();
         }
         if (equals == null) {
           equals = _defaultEquals;
@@ -520,7 +518,7 @@ class LinkedHashMap<K, V> {
   }
 
   @patch
-  factory LinkedHashMap.identity() = _LinkedIdentityHashMap<K, V>.es6;
+  factory LinkedHashMap.identity() = _LinkedIdentityHashMap<K, V>;
 
   // Private factory constructor called by generated code for map literals.
   @NoInline()
@@ -546,20 +544,8 @@ class LinkedHashMap<K, V> {
       fillLiteralMap(keyValuePairs, new JsLinkedHashMap());
 }
 
+// TODO(floitsch): use ES6 Maps when available.
 class _LinkedIdentityHashMap<K, V> extends JsLinkedHashMap<K, V> {
-  static bool get _supportsEs6Maps {
-    return JS('returns:bool;depends:none;effects:none;throws:never;gvn:true',
-              'typeof Map != "undefined"');
-  }
-
-  factory _LinkedIdentityHashMap.es6() {
-    return (_USE_ES6_MAPS && _LinkedIdentityHashMap._supportsEs6Maps)
-        ? new _LinkedIdentityHashMap<K, V>()
-        : new _Es6LinkedIdentityHashMap<K, V>();
-  }
-
-  _LinkedIdentityHashMap();
-
   int internalComputeHashCode(var key) {
     // We force the hash codes to be unsigned 30-bit integers to avoid
     // issues with problematic keys like '__proto__'. Another option
@@ -578,164 +564,6 @@ class _LinkedIdentityHashMap<K, V> extends JsLinkedHashMap<K, V> {
   }
 }
 
-class _Es6LinkedIdentityHashMap<K, V>
-    implements LinkedHashMap<K, V>, InternalMap {
-  final _map;
-  int _modifications = 0;
-
-  _Es6LinkedIdentityHashMap() : _map = JS('var', 'new Map()');
-
-  int get length => JS('int', '#.size', _map);
-  bool get isEmpty => length == 0;
-  bool get isNotEmpty => !isEmpty;
-
-  Iterable<K> get keys => new _Es6MapIterable<K>(this, true);
-
-  Iterable<V> get values =>
-      new _Es6MapIterable<V>(this, false);
-
-  bool containsKey(Object key) {
-    return JS('bool', '#.has(#)', _map, key);
-  }
-
-  bool containsValue(Object value) {
-    return values.any((each) => each == value);
-  }
-
-  void addAll(Map<K, V> other) {
-    other.forEach((K key, V value) {
-      this[key] = value;
-      _modified();
-    });
-  }
-
-  V operator[](Object key) {
-    return JS('var', '#.get(#)', _map, key);
-  }
-
-  void operator[]=(K key, V value) {
-    JS('var', '#.set(#, #)', _map, key, value);
-    _modified();
-  }
-
-  V putIfAbsent(K key, V ifAbsent()) {
-    if (containsKey(key)) return this[key];
-    V value = ifAbsent();
-    this[key] = value;
-    _modified();
-    return value;
-  }
-
-  V remove(Object key) {
-    V value = this[key];
-    JS('bool', '#.delete(#)', _map, key);
-    _modified();
-    return value;
-  }
-
-  void clear() {
-    JS('void', '#.clear()', _map);
-    _modified();
-  }
-
-  void forEach(void action(K key, V value)) {
-    var jsEntries = JS('var', '#.entries()', _map);
-    int modifications = _modifications;
-    while (true) {
-      var next = JS('var', '#.next()', jsEntries);
-      bool done = JS('bool', '#.done', next);
-      if (done) break;
-      var entry = JS('var', '#.value', next);
-      var key = JS('var', '#[0]', entry);
-      var value = JS('var', '#[1]', entry);
-      action(key, value);
-      if (modifications != _modifications) {
-        throw new ConcurrentModificationError(this);
-      }
-    }
-  }
-
-  void _modified() {
-    // Value cycles after 2^30 modifications. If you keep hold of an
-    // iterator for that long, you might miss a modification
-    // detection, and iteration can go sour. Don't do that.
-    _modifications = (_modifications + 1) & 0x3ffffff;
-  }
-
-  String toString() => Maps.mapToString(this);
-}
-
-class _Es6MapIterable<E> extends Iterable<E>
-                         implements EfficientLength {
-  final _map;
-  final bool _isKeys;
-
-  _Es6MapIterable(this._map, this._isKeys);
-
-  int get length => _map.length;
-  bool get isEmpty => _map.isEmpty;
-
-  Iterator<E> get iterator =>
-      new _Es6MapIterator<E>(_map, _map._modifications, _isKeys);
-
-  bool contains(Object element) => _map.containsKey(element);
-
-  void forEach(void f(E element)) {
-    var jsIterator;
-    if (_isKeys) {
-      jsIterator = JS('var', '#.keys()', _map._map);
-    } else {
-      jsIterator = JS('var', '#.values()', _map._map);
-    }
-    int modifications = _map.modifications;
-    while (true) {
-      var next = JS('var', '#.next()', jsIterator);
-      bool done = JS('bool', '#.done', next);
-      if (done) break;
-      var value = JS('var', '#.value', next);
-      f(value);
-      if (modifications != _map.modifications) {
-        throw new ConcurrentModificationError(_map);
-      }
-    }
-  }
-}
-
-class _Es6MapIterator<E> implements Iterator<E> {
-  final _map;
-  final int _modifications;
-  final bool _isKeys;
-  var _jsIterator;
-  var _next;
-  E _current;
-
-  _Es6MapIterator(this._map, this._modifications, this._isKeys) {
-    if (_isKeys) {
-      _jsIterator = JS('var', '#.keys()', _map._map);
-    } else {
-      _jsIterator = JS('var', '#.values()', _map._map);
-    }
-    _next = JS('var', '#.next()', _jsIterator);
-  }
-
-  E get current => _current;
-
-  bool moveNext() {
-    if (_modifications != _map._modifications) {
-      throw new ConcurrentModificationError(_map);
-    }
-    bool done = JS('bool', '#.done', _next);
-    if (done) {
-      _current = null;
-      return false;
-    } else {
-      _current = JS('var', '#.value', _next);
-      _next = JS('var', '#.next()', _jsIterator);
-      return true;
-    }
-  }
-}
-
 // TODO(floitsch): use ES6 maps when available.
 class _LinkedCustomHashMap<K, V> extends JsLinkedHashMap<K, V> {
   final _Equality<K> _equals;