Add dummy dart:html library for documentation.

lib/html/doc/interface/TextAreaElement.dartdoc

+// 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.
+
+// WARNING:
+//   This file contains documentation that is merged into the real source.
+//   Do not make code changes here.
+
+/// @domName HTMLTextAreaElement
+interface TextAreaElement extends Element default _Elements {
+
+  TextAreaElement();
+
+  /** @domName HTMLTextAreaElement.autofocus */
+  bool autofocus;
+
+  /** @domName HTMLTextAreaElement.cols */
+  int cols;
+
+  /** @domName HTMLTextAreaElement.defaultValue */
+  String defaultValue;
+
+  /** @domName HTMLTextAreaElement.disabled */
+  bool disabled;
+
+  /** @domName HTMLTextAreaElement.form */
+  final FormElement form;
+
+  /** @domName HTMLTextAreaElement.labels */
+  final NodeList labels;
+
+  /** @domName HTMLTextAreaElement.maxLength */
+  int maxLength;
+
+  /** @domName HTMLTextAreaElement.name */
+  String name;
+
+  /** @domName HTMLTextAreaElement.placeholder */
+  String placeholder;
+
+  /** @domName HTMLTextAreaElement.readOnly */
+  bool readOnly;
+
+  /** @domName HTMLTextAreaElement.required */
+  bool required;
+
+  /** @domName HTMLTextAreaElement.rows */
+  int rows;
+
+  /** @domName HTMLTextAreaElement.selectionDirection */
+  String selectionDirection;
+
+  /** @domName HTMLTextAreaElement.selectionEnd */
+  int selectionEnd;
+
+  /** @domName HTMLTextAreaElement.selectionStart */
+  int selectionStart;
+
+  /** @domName HTMLTextAreaElement.textLength */
+  final int textLength;
+
+  /** @domName HTMLTextAreaElement.type */
+  final String type;
+
+  /** @domName HTMLTextAreaElement.validationMessage */
+  final String validationMessage;
+
+  /** @domName HTMLTextAreaElement.validity */
+  final ValidityState validity;
+
+  /** @domName HTMLTextAreaElement.value */
+  String value;
+
+  /** @domName HTMLTextAreaElement.willValidate */
+  final bool willValidate;
+
+  /** @domName HTMLTextAreaElement.wrap */
+  String wrap;
+
+  /** @domName HTMLTextAreaElement.checkValidity */
+  bool checkValidity();
+
+  /** @domName HTMLTextAreaElement.select */
+  void select();
+
+  /** @domName HTMLTextAreaElement.setCustomValidity */
+  void setCustomValidity(String error);
+
+  /** @domName HTMLTextAreaElement.setSelectionRange */
+  void setSelectionRange(int start, int end, [String direction]);
+}