Remove stale files from lib/html/src.

lib/html/src/OverflowEvent.dart

Index: lib/html/src/OverflowEvent.dart
diff --git a/lib/html/src/OverflowEvent.dart b/lib/html/src/OverflowEvent.dart
deleted file mode 100644
index da58a27b63470e875a2a0de130f95e889258a4ad..0000000000000000000000000000000000000000
--- a/lib/html/src/OverflowEvent.dart
+++ /dev/null
@@ -1,20 +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.
-
-interface OverflowEvent extends Event default OverflowEventWrappingImplementation {
-
-  OverflowEvent(int orient, bool horizontalOverflow, bool verticalOverflow);
-
-  static const int BOTH = 2;
-
-  static const int HORIZONTAL = 0;
-
-  static const int VERTICAL = 1;
-
-  bool get horizontalOverflow();
-
-  int get orient();
-
-  bool get verticalOverflow();
-}