Add dummy dart:html library for documentation.

lib/html/doc/interface/IDBKeyRange.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 IDBKeyRange
+interface IDBKeyRange default _IDBKeyRangeFactoryProvider {
+
+  /**
+   * @domName IDBKeyRange.only
+   */
+  IDBKeyRange.only(/*IDBKey*/ value);
+
+  /**
+   * @domName IDBKeyRange.lowerBound
+   */
+  IDBKeyRange.lowerBound(/*IDBKey*/ bound, [bool open]);
+
+  /**
+   * @domName IDBKeyRange.upperBound
+   */
+  IDBKeyRange.upperBound(/*IDBKey*/ bound, [bool open]);
+
+  /**
+   * @domName IDBKeyRange.bound
+   */
+  IDBKeyRange.bound(/*IDBKey*/ lower, /*IDBKey*/ upper,
+                    [bool lowerOpen, bool upperOpen]);
+
+
+  /** @domName IDBKeyRange.lower */
+  final Dynamic lower;
+
+  /** @domName IDBKeyRange.lowerOpen */
+  final bool lowerOpen;
+
+  /** @domName IDBKeyRange.upper */
+  final Dynamic upper;
+
+  /** @domName IDBKeyRange.upperOpen */
+  final bool upperOpen;
+}