Use float for scroll offset.

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

 /*
  * Copyright (C) 2013 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 3867 matching lines @@
 }
 
 bool LayoutBlockFlow::hitTestFloats(HitTestResult& result,
                                     const HitTestLocation& locationInContainer,
                                     const LayoutPoint& accumulatedOffset) {
   if (!m_floatingObjects)
     return false;
 
   LayoutPoint adjustedLocation = accumulatedOffset;
   if (isLayoutView()) {
-    DoublePoint position =
-        toLayoutView(this)->frameView()->scrollPositionDouble();
-    adjustedLocation.move(position.x(), position.y());
+    ScrollOffset offset = toLayoutView(this)->frameView()->scrollOffset();
+    adjustedLocation.move(LayoutSize(offset));
   }
 
   const FloatingObjectSet& floatingObjectSet = m_floatingObjects->set();
   FloatingObjectSetIterator begin = floatingObjectSet.begin();
   for (FloatingObjectSetIterator it = floatingObjectSet.end(); it != begin;) {
     --it;
     const FloatingObject& floatingObject = *it->get();
     if (floatingObject.shouldPaint()) {
       LayoutUnit xOffset = xPositionForFloatIncludingMargin(floatingObject) -
                            floatingObject.layoutObject()->location().x();
@@ skipping 285 matching lines @@
 
   ASSERT(dialog->getCenteringMode() == HTMLDialogElement::NeedsCentering);
   if (!canCenterDialog) {
     dialog->setNotCentered();
     return;
   }
 
   FrameView* frameView = document().view();
   LayoutUnit top = LayoutUnit((style()->position() == FixedPosition)
                                   ? 0
-                                  : frameView->scrollOffset().height());
+                                  : frameView->scrollOffsetInt().height());
   int visibleHeight = frameView->visibleContentRect(IncludeScrollbars).height();
   if (size().height() < visibleHeight)
     top += (visibleHeight - size().height()) / 2;
   setY(top);
   dialog->setCentered(top);
 }
 
 void LayoutBlockFlow::simplifiedNormalFlowInlineLayout() {
   ASSERT(childrenInline());
   ListHashSet<RootInlineBox*> lineBoxes;
@@ skipping 255 matching lines @@
   return LayoutBlock::invalidatePaintIfNeeded(paintInvalidationState);
 }
 
 void LayoutBlockFlow::invalidateDisplayItemClients(
     PaintInvalidationReason invalidationReason) const {
   BlockFlowPaintInvalidator(*this).invalidateDisplayItemClients(
       invalidationReason);
 }
 
 }  // namespace blink