Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/TransitionEvent.dartdoc

Index: lib/html/doc/interface/TransitionEvent.dartdoc
diff --git a/lib/html/doc/interface/TransitionEvent.dartdoc b/lib/html/doc/interface/TransitionEvent.dartdoc
deleted file mode 100644
index fd38ae4d43c52301faf6289c2e34b35795efe40f..0000000000000000000000000000000000000000
--- a/lib/html/doc/interface/TransitionEvent.dartdoc
+++ /dev/null
@@ -1,17 +0,0 @@
-// 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 WebKitTransitionEvent
-interface TransitionEvent extends Event {
-
-  /** @domName WebKitTransitionEvent.elapsedTime */
-  final num elapsedTime;
-
-  /** @domName WebKitTransitionEvent.propertyName */
-  final String propertyName;
-}