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 15cf85ca4d22ebf5fc293bb01350c8a37c6b3372..da27efab8511f7945366a386a4eb99b171303ff4 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;
@@ -170,9 +171,6 @@ public:
     void scrollIntoView(bool alignToTop = true);
     void scrollIntoViewIfNeeded(bool centerIfNeeded = true);
 
-    void distributeScroll(ScrollState&);
-    void applyScroll(ScrollState&);
-
     int offsetLeft();
     int offsetTop();
     int offsetWidth();
@@ -370,6 +368,17 @@ public:
     virtual void focus(bool restorePreviousSelection = true, WebFocusType = WebFocusTypeNone);
     virtual void updateFocusAppearance(bool restorePreviousSelection);
     virtual void blur();
+
+    void setDistributeScroll(ScrollStateCallback*);
+    ScriptValue distributeScroll(ScriptState*);

[haraken, 2015/06/30 07:08:30]

Would it be possible to:

- make distributeScroll return ScriptStateCallback*
- let the binding layer call toV8(distributeScroll()), which converts the
ScriptStateCallback* to a V8 wrapper

This is a common way to convert a DOM object to a V8 wrapper. You can define the
toV8 method in ToV8.h.

+    void nativeDistributeScroll(ScrollState&);
+    void setApplyScroll(ScrollStateCallback*);
+    ScriptValue applyScroll(ScriptState*);

[haraken, 2015/06/30 07:08:30]

Ditto.

+    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