Remove the (already disabled) OverflowChangedEvent runtime flag

Source/core/events/OverflowEventInit.idl

Index: Source/core/events/OverflowEventInit.idl
diff --git a/Source/core/events/OverflowEventInit.idl b/Source/core/events/OverflowEventInit.idl
deleted file mode 100644
index 2d53f6c683d63cb469e8f3823c2f82ced83248f4..0000000000000000000000000000000000000000
--- a/Source/core/events/OverflowEventInit.idl
+++ /dev/null
@@ -1,12 +0,0 @@
-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// TODO(philipj): Remove the overflowchanged event. crbug.com/460822
-[
-    RuntimeEnabled=OverflowChangedEvent,
-] dictionary OverflowEventInit : EventInit {
-    unsigned short orient;
-    boolean horizontalOverflow;
-    boolean verticalOverflow;
-};