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

Source/core/page/scrolling/ScrollCustomizationCallbacks.h

+// Copyright 2015 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.
+
+#ifndef ScrollCustomizationCallbacks_h
+#define ScrollCustomizationCallbacks_h
+
+#include "core/CoreExport.h"
+#include "core/dom/Element.h"
+#include "platform/heap/Handle.h"
+#include "wtf/HashMap.h"
+
+namespace blink {
+
+class ScrollStateCallback;
+
+class CORE_EXPORT ScrollCustomizationCallbacks : public GarbageCollected<ScrollCustomizationCallbacks> {
+    WTF_MAKE_NONCOPYABLE(ScrollCustomizationCallbacks);
+
+public:
+    ScrollCustomizationCallbacks() {}
+    void setDistributeScroll(Element*, ScrollStateCallback*);
+    ScrollStateCallback* getDistributeScroll(Element*);
+    void setApplyScroll(Element*, ScrollStateCallback*);
+    ScrollStateCallback* getApplyScroll(Element*);
+
+    DEFINE_INLINE_TRACE()
+    {
+        visitor->trace(m_applyScrollCallbacks);
+        visitor->trace(m_distributeScrollCallbacks);
+    };
+
+#if !ENABLE(OILPAN)
+    void removeCallbacksForElement(Element*);
+#endif
+
+private:
+    using ScrollStateCallbackList = HeapHashMap<RawPtrWillBeWeakMember<Element>, Member<ScrollStateCallback>>;
+    ScrollStateCallbackList m_applyScrollCallbacks;
+    ScrollStateCallbackList m_distributeScrollCallbacks;
+};
+
+} // namespace blink
+
+#endif // ScrollCustomizationCallbacks_h