Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/Performance.dartdoc

Index: lib/html/doc/interface/Performance.dartdoc
diff --git a/lib/html/doc/interface/Performance.dartdoc b/lib/html/doc/interface/Performance.dartdoc
deleted file mode 100644
index 1e036b8f9923cdb494e3d6b4a2b9af61eb3a67b1..0000000000000000000000000000000000000000
--- a/lib/html/doc/interface/Performance.dartdoc
+++ /dev/null
@@ -1,23 +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 Performance
-interface Performance {
-
-  /** @domName Performance.memory */
-  final MemoryInfo memory;
-
-  /** @domName Performance.navigation */
-  final PerformanceNavigation navigation;
-
-  /** @domName Performance.timing */
-  final PerformanceTiming timing;
-
-  /** @domName Performance.webkitNow */
-  num webkitNow();
-}