Remove stale files from lib/html/src.

lib/html/src/DeviceOrientationEvent.dart

Index: lib/html/src/DeviceOrientationEvent.dart
diff --git a/lib/html/src/DeviceOrientationEvent.dart b/lib/html/src/DeviceOrientationEvent.dart
deleted file mode 100644
index 3447be42b7e0f39ba7bad555942d35faa8201695..0000000000000000000000000000000000000000
--- a/lib/html/src/DeviceOrientationEvent.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 DeviceOrientationEvent extends Event default DeviceOrientationEventWrappingImplementation {
-
-  DeviceOrientationEvent(String type, double alpha, double beta, double gamma,
-      [bool canBubble, bool cancelable]);
-
-  num get alpha();
-
-  num get beta();
-
-  num get gamma();
-}