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

Source/core/dom/Element.h

Index: Source/core/dom/Element.h
diff --git a/Source/core/dom/Element.h b/Source/core/dom/Element.h
index 4c1dfb9c982316e552c490dd13247286aaa8e48a..bc979086f99f844ec713b008de273a9f77d05d53 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -62,6 +62,7 @@ class MutableStylePropertySet;
 class PropertySetCSSStyleDeclaration;
 class PseudoElement;
 class ScrollState;
+class ScrollStateCallback;
 class ScrollToOptions;
 class ShadowRoot;
 class ShadowRootInit;
@@ -172,9 +173,6 @@ public:
     void scrollIntoView(bool alignToTop = true);
     void scrollIntoViewIfNeeded(bool centerIfNeeded = true);
 
-    void distributeScroll(ScrollState&);
-    void applyScroll(ScrollState&);
-
     int offsetLeft();
     int offsetTop();
     int offsetWidth();
@@ -380,6 +378,17 @@ public:
     virtual void focus(bool restorePreviousSelection = true, WebFocusType = WebFocusTypeNone, InputDevice* sourceDevice = nullptr);
     virtual void updateFocusAppearance(bool restorePreviousSelection);
     virtual void blur();
+
+    static void removeScrollCustomizationCallbacksForDocument(Document*);
+
+    void setDistributeScroll(ScrollStateCallback*, String nativeScrollBehavior);
+    void nativeDistributeScroll(ScrollState&);
+    void setApplyScroll(ScrollStateCallback*, String nativeScrollBehavior);
+    void nativeApplyScroll(ScrollState&);
+
+    void callDistributeScroll(ScrollState&);
+    void callApplyScroll(ScrollState&);
+
     // Whether this element can receive focus at all. Most elements are not
     // focusable but some elements, such as form controls and links, are. Unlike
     // layoutObjectIsFocusable(), this method may be called when layout is not up to