Fix error in determining the target position for smooth scroll animation curve

third_party/WebKit/Source/platform/scroll/ScrollAnimator.cpp

 /*
  * Copyright (c) 2011, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 43 matching lines @@
     , m_timeFunction(timeFunction)
 {
 }
 
 ScrollAnimator::~ScrollAnimator()
 {
 }
 
 FloatPoint ScrollAnimator::desiredTargetPosition() const
 {
-    return m_animationCurve ? m_targetOffset : currentPosition();
+    return (m_animationCurve || m_runState == RunState::WaitingToSendToCompositor)
+        ? m_targetOffset : currentPosition();
 }
 
 float ScrollAnimator::computeDeltaToConsume(
     ScrollbarOrientation orientation, float pixelDelta) const
 {
     FloatPoint pos = desiredTargetPosition();
     float currentPos = (orientation == HorizontalScrollbar) ? pos.x() : pos.y();
     float newPos = clampScrollPosition(orientation, currentPos + pixelDelta);
     return (currentPos == newPos) ? 0.0f : (newPos - currentPos);
 }
@@ skipping 204 matching lines @@
 {
     reattachCompositorPlayerIfNeeded(timeline);
 }
 
 DEFINE_TRACE(ScrollAnimator)
 {
     ScrollAnimatorBase::trace(visitor);
 }
 
 } // namespace blink