Add dummy dart:html library for documentation.

lib/html/doc/interface/XSLTProcessor.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 XSLTProcessor
+interface XSLTProcessor default _XSLTProcessorFactoryProvider {
+
+  XSLTProcessor();
+
+  /** @domName XSLTProcessor.clearParameters */
+  void clearParameters();
+
+  /** @domName XSLTProcessor.getParameter */
+  String getParameter(String namespaceURI, String localName);
+
+  /** @domName XSLTProcessor.importStylesheet */
+  void importStylesheet(Node stylesheet);
+
+  /** @domName XSLTProcessor.removeParameter */
+  void removeParameter(String namespaceURI, String localName);
+
+  /** @domName XSLTProcessor.reset */
+  void reset();
+
+  /** @domName XSLTProcessor.setParameter */
+  void setParameter(String namespaceURI, String localName, String value);
+
+  /** @domName XSLTProcessor.transformToDocument */
+  Document transformToDocument(Node source);
+
+  /** @domName XSLTProcessor.transformToFragment */
+  DocumentFragment transformToFragment(Node source, Document docVal);
+}