Use float for scroll offset.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Simon Hausmann <hausmann@kde.org>
  *           (C) 2000 Stefan Schimanski (1Stein@gmx.de)
  * Copyright (C) 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. 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
  * License as published by the Free Software Foundation; either
@@ skipping 159 matching lines @@
 
   if (action == HitTestForeground) {
     FrameView* childFrameView = toFrameView(widget());
     LayoutViewItem childRootItem = childFrameView->layoutViewItem();
 
     if (visibleToHitTestRequest(result.hitTestRequest()) &&
         !childRootItem.isNull()) {
       LayoutPoint adjustedLocation = accumulatedOffset + location();
       LayoutPoint contentOffset = LayoutPoint(borderLeft() + paddingLeft(),
                                               borderTop() + paddingTop()) -
-                                  LayoutSize(childFrameView->scrollOffset());
+                                  LayoutSize(childFrameView->scrollOffsetInt());
       HitTestLocation newHitTestLocation(locationInContainer,
                                          -adjustedLocation - contentOffset);
       HitTestRequest newHitTestRequest(result.hitTestRequest().type() |
                                        HitTestRequest::ChildFrameHitTest);
       HitTestResult childFrameResult(newHitTestRequest, newHitTestLocation);
 
       // The frame's layout and style must be up to date if we reach here.
       bool isInsideChildFrame =
           childRootItem.hitTestNoLifecycleUpdate(childFrameResult);
 
@@ skipping 191 matching lines @@
 }
 
 bool LayoutPart::isThrottledFrameView() const {
   if (!widget() || !widget()->isFrameView())
     return false;
   const FrameView* frameView = toFrameView(widget());
   return frameView->shouldThrottleRendering();
 }
 
 }  // namespace blink