Remove stale files from lib/html/src.

lib/html/src/HashChangeEvent.dart

Index: lib/html/src/HashChangeEvent.dart
diff --git a/lib/html/src/HashChangeEvent.dart b/lib/html/src/HashChangeEvent.dart
deleted file mode 100644
index 484f637799c6e4245d6ce0c56e8f102117dfd4c1..0000000000000000000000000000000000000000
--- a/lib/html/src/HashChangeEvent.dart
+++ /dev/null
@@ -1,13 +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 HashChangeEvent extends Event default HashChangeEventWrappingImplementation {
-
-  HashChangeEvent(String type, String oldURL, String newURL, [bool canBubble,
-      bool cancelable]);
-
-  String get newURL();
-
-  String get oldURL();
-}