Use float for scroll offset.

third_party/WebKit/Source/core/layout/LayoutBoxModelObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 766 matching lines @@
                                   localQuad.boundingBox().center(), localQuad);
     containingBlock->mapLocalToAncestor(scrollAncestor, transformState,
                                         ApplyContainerFlip);
     transformState.flatten();
     scrollContainerRelativePaddingBoxRect =
         transformState.lastPlanarQuad().boundingBox();
 
     // The sticky position constraint rects should be independent of the current scroll position, so after
     // mapping we add in the scroll position to get the container's position within the ancestor scroller's
     // unscrolled layout overflow.
-    FloatSize scrollOffset(
+    ScrollOffset scrollOffset(
         scrollAncestor
             ? toFloatSize(
-                  scrollAncestor->getScrollableArea()->offsetFromOrigin())
+                  scrollAncestor->getScrollableArea()->absolutePosition())
             : FloatSize());
     scrollContainerRelativePaddingBoxRect.move(scrollOffset);
   }
 
   LayoutRect scrollContainerRelativeContainingBlockRect(
       scrollContainerRelativePaddingBoxRect);
   // This is removing the padding of the containing block's overflow rect to get the flow
   // box rectangle and removing the margin of the sticky element to ensure that space between
   // the sticky element and its containing flow box. It is an open issue whether the margin
   // should collapse (See https://www.w3.org/TR/css-position-3/#sticky-pos).
@@ skipping 100 matching lines @@
 
 FloatRect LayoutBoxModelObject::computeStickyConstrainingRect() const {
   if (layer()->ancestorOverflowLayer()->isRootLayer())
     return view()->frameView()->visibleContentRect();
 
   LayoutBox* enclosingClippingBox =
       toLayoutBox(layer()->ancestorOverflowLayer()->layoutObject());
   FloatRect constrainingRect;
   constrainingRect =
       FloatRect(enclosingClippingBox->overflowClipRect(LayoutPoint(DoublePoint(
-          enclosingClippingBox->getScrollableArea()->offsetFromOrigin()))));
+          enclosingClippingBox->getScrollableArea()->absolutePosition()))));
   constrainingRect.move(enclosingClippingBox->paddingLeft(),
                         enclosingClippingBox->paddingTop());
   constrainingRect.contract(
       FloatSize(enclosingClippingBox->paddingLeft() +
                     enclosingClippingBox->paddingRight(),
                 enclosingClippingBox->paddingTop() +
                     enclosingClippingBox->paddingBottom()));
   return constrainingRect;
 }
 
@@ skipping 406 matching lines @@
   if (rootElementStyle->hasBackground())
     return false;
 
   if (node() != document().firstBodyElement())
     return false;
 
   return true;
 }
 
 }  // namespace blink