Unifies ScrollView and RenderLayer to use non-shifted [minPos, maxPos] scroll offset

Source/core/platform/mac/ScrollAnimatorMac.mm

 /*
  * Copyright (C) 2010, 2011 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 648 matching lines @@
 {
     m_haveScrolledSincePageLoad = true;
 
     if (!scrollAnimationEnabledForSystem() || !m_scrollableArea->scrollAnimatorEnabled())
         return ScrollAnimator::scroll(orientation, granularity, step, multiplier);
 
     if (granularity == ScrollByPixel)
         return ScrollAnimator::scroll(orientation, granularity, step, multiplier);
 
     float currentPos = orientation == HorizontalScrollbar ? m_currentPosX : m_currentPosY;
-    float newPos = std::max<float>(std::min<float>(currentPos + (step * multiplier), static_cast<float>(m_scrollableArea->scrollSize(orientation))), 0);
+    float newPos = std::max<float>(std::min<float>(currentPos + (step * multiplier), m_scrollableArea->maximumScrollPosition(orientation)), m_scrollableArea->minimumScrollPosition(orientation));
     if (currentPos == newPos)
         return false;
 
     NSPoint newPoint;
     if ([m_scrollAnimationHelper.get() _isAnimating]) {
         NSPoint targetOrigin = [m_scrollAnimationHelper.get() targetOrigin];
         newPoint = orientation == HorizontalScrollbar ? NSMakePoint(newPos, targetOrigin.y) : NSMakePoint(targetOrigin.x, newPos);
     } else
         newPoint = orientation == HorizontalScrollbar ? NSMakePoint(newPos, m_currentPosY) : NSMakePoint(m_currentPosX, newPos);
 
     [m_scrollAnimationHelper.get() scrollToPoint:newPoint];
     return true;
 }
 
 void ScrollAnimatorMac::scrollToOffsetWithoutAnimation(const FloatPoint& offset)
 {
     [m_scrollAnimationHelper.get() _stopRun];
     immediateScrollTo(offset);
 }
 
 FloatPoint ScrollAnimatorMac::adjustScrollPositionIfNecessary(const FloatPoint& position) const
 {
     if (!m_scrollableArea->constrainsScrollingToContentEdge())
         return position;
 
-    float newX = max<float>(min<float>(position.x(), m_scrollableArea->contentsSize().width() - m_scrollableArea->visibleWidth()), 0);
-    float newY = max<float>(min<float>(position.y(), m_scrollableArea->contentsSize().height() - m_scrollableArea->visibleHeight()), 0);
+    IntPoint minPos = m_scrollableArea->minimumScrollPosition();
+    IntPoint maxPos = m_scrollableArea->maximumScrollPosition();
+
+    float newX = max<float>(min<float>(position.x(), maxPos.x()), minPos.x());
+    float newY = max<float>(min<float>(position.y(), maxPos.y()), minPos.y());
 
     return FloatPoint(newX, newY);
 }
 
 void ScrollAnimatorMac::immediateScrollTo(const FloatPoint& newPosition)
 {
     FloatPoint adjustedPosition = adjustScrollPositionIfNecessary(newPosition);
  
     bool positionChanged = adjustedPosition.x() != m_currentPosX || adjustedPosition.y() != m_currentPosY;
     if (!positionChanged && !scrollableArea()->scrollOriginChanged())
@@ skipping 576 matching lines @@
     if (Scrollbar* verticalScrollbar = m_scrollableArea->verticalScrollbar())
         rectInViewCoordinates = verticalScrollbar->convertToContainingView(scrollerThumb);
 
     if (rectInViewCoordinates == m_visibleScrollerThumbRect)
         return;
 
     m_visibleScrollerThumbRect = rectInViewCoordinates;
 }
 
 } // namespace WebCore