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

Source/core/page/scrolling/ScrollStateCallback.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 ScrollStateCallback_h
+#define ScrollStateCallback_h
+
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class ScrollState;
+
+enum class NativeScrollBehavior {
+    DisableNativeScroll,
+    PerformBeforeNativeScroll,
+    PerformAfterNativeScroll,
+};
+
+class ScrollStateCallback : public GarbageCollectedFinalized<ScrollStateCallback> {
+public:
+    ScrollStateCallback()
+        : m_nativeScrollBehavior(NativeScrollBehavior::DisableNativeScroll)
+    {
+    }
+
+    virtual ~ScrollStateCallback()
+    {
+    }
+
+    DEFINE_INLINE_VIRTUAL_TRACE() {}
+    virtual void handleEvent(ScrollState*) = 0;
+
+    void setNativeScrollBehavior(NativeScrollBehavior nativeScrollBehavior)
+    {
+        m_nativeScrollBehavior = nativeScrollBehavior;
+    }
+
+    NativeScrollBehavior nativeScrollBehavior()
+    {
+        return m_nativeScrollBehavior;
+    }
+
+    static NativeScrollBehavior toNativeScrollBehavior(String nativeScrollBehavior);
+
+protected:
+    NativeScrollBehavior m_nativeScrollBehavior;
+};
+
+} // namespace blink
+
+#endif // ScrollStateCallback_h