Use viewportConstrainedVisibleContentRect() to get the scrolling offset

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 1289 matching lines @@
         }
         if (heightChanged) {
             if (style->height().isFixed() && (style->top().isAuto() || style->bottom().isAuto()))
                 renderer->setNeedsPositionedMovementLayout();
             else
                 renderer->setNeedsLayoutAndFullPaintInvalidation();
         }
     }
 }
 
-IntSize FrameView::scrollOffsetForFixedPosition() const
+IntSize FrameView::scrollOffsetForViewportConstrainedObjects() const
 {
-    return toIntSize(clampScrollPosition(scrollPosition()));
+    return roundedIntSize(viewportConstrainedVisibleContentRect().location());
 }
 
 IntPoint FrameView::lastKnownMousePosition() const
 {
     return m_frame->eventHandler().lastKnownMousePosition();
 }
 
 bool FrameView::shouldSetCursor() const
 {
     Page* page = frame().page();
@@ skipping 2646 matching lines @@
         return;
 
     ScrollableArea::setScrollOrigin(origin);
 
     // Update if the scroll origin changes, since our position will be different if the content size did not change.
     if (updatePositionAtAll && updatePositionSynchronously)
         updateScrollbars(scrollOffsetDouble());
 }
 
 } // namespace blink