Remove stale files from lib/html/src.

lib/html/src/CompositionEvent.dart

Index: lib/html/src/CompositionEvent.dart
diff --git a/lib/html/src/CompositionEvent.dart b/lib/html/src/CompositionEvent.dart
deleted file mode 100644
index 7f6c8cf8b9ba0f0e42c634bdf0334f79848cf56f..0000000000000000000000000000000000000000
--- a/lib/html/src/CompositionEvent.dart
+++ /dev/null
@@ -1,11 +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 CompositionEvent extends UIEvent default CompositionEventWrappingImplementation {
-
-  CompositionEvent(String type, Window view, String data, [bool canBubble,
-      bool cancelable]);
-
-  String get data();
-}