Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/StorageInfoUsageCallback.dartdoc

Index: lib/html/doc/interface/StorageInfoUsageCallback.dartdoc
diff --git a/lib/html/doc/interface/StorageInfoUsageCallback.dartdoc b/lib/html/doc/interface/StorageInfoUsageCallback.dartdoc
deleted file mode 100644
index a97b3e8fd5bdd9db955a8dc759912dfc1dbd55e2..0000000000000000000000000000000000000000
--- a/lib/html/doc/interface/StorageInfoUsageCallback.dartdoc
+++ /dev/null
@@ -1,9 +0,0 @@
-// Copyright (c) 2011, 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.
-
-typedef bool StorageInfoUsageCallback(int currentUsageInBytes, int currentQuotaInBytes);