Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/Counter.dartdoc

Index: lib/html/doc/interface/Counter.dartdoc
diff --git a/lib/html/doc/interface/Counter.dartdoc b/lib/html/doc/interface/Counter.dartdoc
deleted file mode 100644
index 427789d95e53e4a3773b27f46bb494c6687c1c3f..0000000000000000000000000000000000000000
--- a/lib/html/doc/interface/Counter.dartdoc
+++ /dev/null
@@ -1,20 +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 Counter
-interface Counter {
-
-  /** @domName Counter.identifier */
-  final String identifier;
-
-  /** @domName Counter.listStyle */
-  final String listStyle;
-
-  /** @domName Counter.separator */
-  final String separator;
-}