Expose scroll customization for touch to JS (behind REF).

Source/core/page/scrolling/ScrollStateCallback.idl

Index: Source/core/page/scrolling/ScrollStateCallback.idl
diff --git a/Source/core/input/InputDeviceInit.idl b/Source/core/page/scrolling/ScrollStateCallback.idl
similarity index 52%
copy from Source/core/input/InputDeviceInit.idl
copy to Source/core/page/scrolling/ScrollStateCallback.idl
index cad1069a92f780de0da7dc4200c699fd61beca74..3a9ee0e54f8d4c4e1e048ad622b5fbaf75f36b8e 100644
--- a/Source/core/input/InputDeviceInit.idl
+++ b/Source/core/page/scrolling/ScrollStateCallback.idl
@@ -2,8 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// https://goo.gl/1ipTpP
+
 [
-    RuntimeEnabled=InputDevice,
-] dictionary InputDeviceInit {
-    boolean firesTouchEvents = false;
+    RuntimeEnabled=ScrollCustomization
+] callback interface ScrollStateCallback {
+    void handleEvent(ScrollState scrollState);
 };