Use scroll customization primitives for touch scrolling (behind REF).

Source/core/page/scrolling/ScrollState.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/ScrollState.h"
 
 #include "core/dom/Element.h"
 #include "core/dom/ExceptionCode.h"
 
 namespace blink {
 
 PassRefPtrWillBeRawPtr<ScrollState> ScrollState::create(double deltaX, double deltaY,
     double deltaGranularity, double velocityX, double velocityY, bool inInertialPhase,
-    bool isEnding, bool fromUserInput, bool shouldPropagate,
+    bool isBeginning, bool isEnding, bool fromUserInput, bool shouldPropagate,
     bool deltaConsumedForScrollSequence)
 {
     return adoptRefWillBeNoop(new ScrollState(
         deltaX, deltaY, deltaGranularity, velocityX, velocityY,
-        inInertialPhase, isEnding, fromUserInput, shouldPropagate,
+        inInertialPhase, isBeginning, isEnding, fromUserInput, shouldPropagate,
         deltaConsumedForScrollSequence));
 }
 
 ScrollState::ScrollState(double deltaX, double deltaY, double deltaGranularity,
-    double velocityX, double velocityY, bool inInertialPhase, bool isEnding,
-    bool fromUserInput, bool shouldPropagate, bool deltaConsumedForScrollSequence)
+    double velocityX, double velocityY, bool inInertialPhase, bool isBeginning,
+    bool isEnding, bool fromUserInput, bool shouldPropagate,
+    bool deltaConsumedForScrollSequence)
     : m_deltaX(deltaX)
     , m_deltaY(deltaY)
     , m_deltaGranularity(deltaGranularity)
     , m_velocityX(velocityX)
     , m_velocityY(velocityY)
     , m_inInertialPhase(inInertialPhase)
+    , m_isBeginning(isBeginning)
     , m_isEnding(isEnding)
     , m_fromUserInput(fromUserInput)
     , m_shouldPropagate(shouldPropagate)
     , m_deltaConsumedForScrollSequence(deltaConsumedForScrollSequence)
 {
 }
 
 void ScrollState::consumeDelta(double x, double y, ExceptionState& exceptionState)
 {
     if ((m_deltaX > 0 && 0 > x) || (m_deltaX < 0 && 0 < x) || (m_deltaY > 0 && 0 > y) || (m_deltaY < 0 && 0 < y)) {
         exceptionState.throwDOMException(InvalidModificationError, "Can't increase delta using consumeDelta");
         return;
     }
     if (fabs(x) > fabs(m_deltaX) || fabs(y) > fabs(m_deltaY)) {
         exceptionState.throwDOMException(InvalidModificationError, "Can't change direction of delta using consumeDelta");
         return;
     }
     consumeDeltaNative(x, y);
 }
 
+void ScrollState::distributeToScrollChainDescendant()
+{
+    if (!m_scrollChain.isEmpty())
+        m_scrollChain.takeFirst()->distributeScroll(*this);
+}
+
 void ScrollState::consumeDeltaNative(double x, double y)
 {
     m_deltaX -= x;
     m_deltaY -= y;
 
     if (x || y)
         m_deltaConsumedForScrollSequence = true;
 }
 
 } // namespace blink