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

Source/core/page/scrolling/ScrollCustomizationCallbacks.cpp

+// 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.
+
+#include "config.h"
+#include "core/page/scrolling/ScrollCustomizationCallbacks.h"
+
+#include "core/page/scrolling/ScrollStateCallback.h"
+#include "wtf/Deque.h"
+
+namespace blink {
+
+void ScrollCustomizationCallbacks::setDistributeScroll(Element* element, ScrollStateCallback* scrollStateCallback)
+{
+    m_distributeScrollCallbacks.set(element, scrollStateCallback);

[haraken, 2015/08/28 00:14:13]

If multiple callbacks are installed on an element, the old callback will be
overwritten. Is it expected?

+}
+
+ScrollStateCallback* ScrollCustomizationCallbacks::getDistributeScroll(Element* element)
+{
+    auto it = m_distributeScrollCallbacks.find(element);
+    if (it == m_distributeScrollCallbacks.end())
+        return nullptr;
+    return it->value.get();
+}
+
+void ScrollCustomizationCallbacks::setApplyScroll(Element* element, ScrollStateCallback* scrollStateCallback)
+{
+    m_applyScrollCallbacks.set(element, scrollStateCallback);

[haraken, 2015/08/28 00:14:13]

Ditto.

+}
+
+ScrollStateCallback* ScrollCustomizationCallbacks::getApplyScroll(Element* element)
+{
+    auto it = m_applyScrollCallbacks.find(element);
+    if (it == m_applyScrollCallbacks.end())
+        return nullptr;
+    return it->value.get();
+}
+
+#if !ENABLE(OILPAN)
+void ScrollCustomizationCallbacks::removeCallbacksForElement(Element* element)
+{
+    m_applyScrollCallbacks.remove(element);
+    m_distributeScrollCallbacks.remove(element);
+}
+#endif
+
+} // namespace blink