Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/ProgressEvent.dartdoc

Index: lib/html/doc/interface/ProgressEvent.dartdoc
diff --git a/lib/html/doc/interface/ProgressEvent.dartdoc b/lib/html/doc/interface/ProgressEvent.dartdoc
deleted file mode 100644
index c33b15c2f6c3ad1daf6e24fe1af8ea6a44d8a1a6..0000000000000000000000000000000000000000
--- a/lib/html/doc/interface/ProgressEvent.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 ProgressEvent
-interface ProgressEvent extends Event {
-
-  /** @domName ProgressEvent.lengthComputable */
-  final bool lengthComputable;
-
-  /** @domName ProgressEvent.loaded */
-  final int loaded;
-
-  /** @domName ProgressEvent.total */
-  final int total;
-}