Port the remaining of dart:coreimpl to the unified corelib.

lib/compiler/implementation/lib/mock.dart

Index: lib/compiler/implementation/lib/mock.dart
diff --git a/lib/compiler/implementation/lib/mock.dart b/lib/compiler/implementation/lib/mock.dart
index d5e601c6756d9f6fa88b4a63743e29dcbbf5f3ba..bc48fea5a19fdcb99c3157cfce7c179787c73833 100644
--- a/lib/compiler/implementation/lib/mock.dart
+++ b/lib/compiler/implementation/lib/mock.dart
@@ -64,42 +64,3 @@ void exit(int exitCode) {
   throw new UnsupportedOperationException("exit($exitCode)");
 }
 
-class _Expando<T> implements Expando<T> {
-
-  final String name;
-
-  const _Expando([this.name]);
-
-  T operator[](Object object) {
-    var values = Primitives.getProperty(object, EXPANDO_PROPERTY_NAME);
-    return (values === null) ? null : Primitives.getProperty(values, _getKey());
-  }
-
-  void operator[]=(Object object, T value) {
-    var values = Primitives.getProperty(object, EXPANDO_PROPERTY_NAME);
-    if (values === null) {
-      values = new Object();
-      Primitives.setProperty(object, EXPANDO_PROPERTY_NAME, values);
-    }
-    Primitives.setProperty(values, _getKey(), value);
-  }
-
-  String toString() {
-    String key = _getKey();
-    return (name === null) ? "Expando:${key}" : "Expando:${name}@${key}";
-  }
-
-  String _getKey() {
-    String key = Primitives.getProperty(this, KEY_PROPERTY_NAME);
-    if (key === null) {
-      key = "expando\$key\$${keyCount++}";
-      Primitives.setProperty(this, KEY_PROPERTY_NAME, key);
-    }
-    return key;
-  }
-
-  static final String KEY_PROPERTY_NAME = 'expando\$key';
-  static final String EXPANDO_PROPERTY_NAME = 'expando\$values';
-  static int keyCount = 0;
-
-}