[mdv] Implement two-way binding to HTMLTextArea.value

pkg/mdv/lib/src/text_area_element.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.
+
+part of mdv;
+
+/** Extensions to the [TextAreaElement] API. */
+class _TextAreaElementExtension extends _ElementExtension {
+  _ValueBinding _valueBinding;
+
+  _TextAreaElementExtension(TextAreaElement node) : super(node);
+
+  TextAreaElement get node => super.node;
+
+  void bind(String name, model, String path) {
+    if (name.toLowerCase() == 'value') {
+      unbind('value');
+      node.attributes.remove('value');
+      _valueBinding = new _ValueBinding(node, model, path);
+    }
+  }
+
+  void unbind(String name) {
+    if (name.toLowerCase() == 'value' && _valueBinding != null) {
+      _valueBinding.unbind();
+      _valueBinding = null;
+    }
+  }
+
+  void unbindAll() {
+    unbind('value');
+    super.unbindAll();
+  }
+}