Implement DragEvent and move MouseEvent.dataTransfer

Source/core/events/DragEventInit.idl

Index: Source/core/events/DragEventInit.idl
diff --git a/Source/core/events/PopStateEventInit.idl b/Source/core/events/DragEventInit.idl
similarity index 53%
copy from Source/core/events/PopStateEventInit.idl
copy to Source/core/events/DragEventInit.idl
index ce7ae0fe79066c4dc7f224c6ce44a35d093f6c12..3b90386dc5af4b8f4335d78669054fe5cc21b7d1 100644
--- a/Source/core/events/PopStateEventInit.idl
+++ b/Source/core/events/DragEventInit.idl
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// https://html.spec.whatwg.org/multipage/browsers.html#the-popstateevent-interface
+// https://html.spec.whatwg.org/multipage/interaction.html#drageventinit
 
-dictionary PopStateEventInit : EventInit {
-    any state;
+dictionary DragEventInit : MouseEventInit {
+    DataTransfer? dataTransfer;
 };