Remove explicit interface versions of dartdoc files.

lib/html/doc/nodoc-src/shared_FactoryProviders.dart

-// 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.
-
-class _EventFactoryProvider {
-  factory Event(String type, [bool canBubble = true,
-                              bool cancelable = true]) => null;
-}
-
-class _MouseEventFactoryProvider {
-  factory MouseEvent(String type, Window view, int detail,
-      int screenX, int screenY, int clientX, int clientY, int button,
-      [bool canBubble = true, bool cancelable = true, bool ctrlKey = false,
-      bool altKey = false, bool shiftKey = false, bool metaKey = false,
-       EventTarget relatedTarget = null]) => null;
-}
-
-class _CSSStyleDeclarationFactoryProvider {
-  factory CSSStyleDeclaration.css(String css) => null;
-  factory CSSStyleDeclaration() => null;
-}
-
-class _DocumentFragmentFactoryProvider {
-  /** @domName Document.createDocumentFragment */
-  factory DocumentFragment() => document.createDocumentFragment();
-  factory DocumentFragment.html(String html) => null;
-  factory DocumentFragment.xml(String xml) => null;
-  factory DocumentFragment.svg(String svg) => null;
-}
-
-class _SVGElementFactoryProvider {
-  factory SVGElement.tag(String tag) => null;
-  factory SVGElement.svg(String svg) => null;
-}
-
-class _SVGSVGElementFactoryProvider {
-  factory SVGSVGElement() => null;
-}