Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/ShadowRoot.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 ShadowRoot
-interface ShadowRoot extends DocumentFragment default _ShadowRootFactoryProvider {
-
-  ShadowRoot(Element host);
-
-  /** @domName ShadowRoot.activeElement */
-  final Element activeElement;
-
-  /** @domName ShadowRoot.applyAuthorStyles */
-  bool applyAuthorStyles;
-
-  /** @domName ShadowRoot.host */
-  final Element host;
-
-  /** @domName ShadowRoot.innerHTML */
-  String innerHTML;
-
-  /** @domName ShadowRoot.getElementById */
-  Element getElementById(String elementId);
-
-  /** @domName ShadowRoot.getElementsByClassName */
-  NodeList getElementsByClassName(String className);
-
-  /** @domName ShadowRoot.getElementsByTagName */
-  NodeList getElementsByTagName(String tagName);
-
-  /** @domName ShadowRoot.getElementsByTagNameNS */
-  NodeList getElementsByTagNameNS(String namespaceURI, String localName);
-
-  /** @domName ShadowRoot.getSelection */
-  DOMSelection getSelection();
-}