Move frog/leg to lib/compiler/implementation.

frog/leg/lib/constant_map.dart

-// Copyright (c) 2012, 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.
-
-// This class has no constructor. This is on purpose since the instantiation
-// is shortcut by the compiler.
-class ConstantMap<V> implements Map<String, V> {
-  final int length;
-  // A constant map is backed by a JavaScript object.
-  final _jsObject;
-  final List<String> _keys;
-
-  bool containsValue(V needle) {
-    return getValues().some((V value) => value == needle);
-  }
-
-  bool containsKey(String key) {
-    if (key == '__proto__') return false;
-    return jsHasOwnProperty(_jsObject, key);
-  }
-
-  V operator [](String key) {
-    if (!containsKey(key)) return null;
-    return jsPropertyAccess(_jsObject, key);
-  }
-
-  void forEach(void f(String key, V value)) {
-    _keys.forEach((String key) => f(key, this[key]));
-  }
-
-  Collection<String> getKeys() => _keys;
-
-  Collection<V> getValues() {
-    List<V> result = <V>[];
-    _keys.forEach((String key) => result.add(this[key]));
-    return result;
-  }
-
-  bool isEmpty() => length == 0;
-
-  String toString() => Maps.mapToString(this);
-
-  _throwImmutable() {
-    throw const IllegalAccessException();
-  }
-  void operator []=(String key, V val) => _throwImmutable();
-  V putIfAbsent(String key, V ifAbsent()) => _throwImmutable();
-  V remove(String key) => _throwImmutable();
-  void clear() => _throwImmutable();
-}