Remove files that have already been ported or do not need to be ported.

client/html/src/EventTarget.dart

Index: client/html/src/EventTarget.dart
diff --git a/client/html/src/EventTarget.dart b/client/html/src/EventTarget.dart
deleted file mode 100644
index 1774cb66c743b44c2997e0fbf13d1ef7fd8ff573..0000000000000000000000000000000000000000
--- a/client/html/src/EventTarget.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 EventListenerList {
-  EventListenerList add(EventListener handler, [bool useCapture]);
-
-  EventListenerList remove(EventListener handler, [bool useCapture]);
-
-  bool dispatch(Event evt);
-}
-
-interface Events {
-  EventListenerList operator [](String type);
-}
-
-interface EventTarget {
-  Events get on();
-}
-