Remove stale files from lib/html/src.

lib/html/src/ProgressEvent.dart

Index: lib/html/src/ProgressEvent.dart
diff --git a/lib/html/src/ProgressEvent.dart b/lib/html/src/ProgressEvent.dart
deleted file mode 100644
index 4964e4ea985b983f17d5b0537064b95eb2b67578..0000000000000000000000000000000000000000
--- a/lib/html/src/ProgressEvent.dart
+++ /dev/null
@@ -1,15 +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 ProgressEvent extends Event default ProgressEventWrappingImplementation {
-
-  ProgressEvent(String type, int loaded, [bool canBubble, bool cancelable,
-      bool lengthComputable, int total]);
-
-  bool get lengthComputable();
-
-  int get loaded();
-
-  int get total();
-}