Use float for scroll offset.

third_party/WebKit/Source/core/dom/TreeScope.cpp

 /*
  * Copyright (C) 2011 Google Inc. All Rights Reserved.
  * Copyright (C) 2012 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
@@ skipping 202 matching lines @@
                                              IntPoint& point) {
   LocalFrame* frame = document.frame();
   if (!frame)
     return false;
   FrameView* frameView = frame->view();
   if (!frameView)
     return false;
 
   FloatPoint pointInDocument(point);
   pointInDocument.scale(frame->pageZoomFactor(), frame->pageZoomFactor());
-  pointInDocument.moveBy(frameView->scrollPosition());
+  pointInDocument.move(frameView->scrollOffset());
   IntPoint roundedPointInDocument = roundedIntPoint(pointInDocument);
 
   if (!frameView->visibleContentRect().contains(roundedPointInDocument))
     return false;
 
   point = roundedPointInDocument;
   return true;
 }
 
 HitTestResult hitTestInDocument(const Document* document,
@@ skipping 307 matching lines @@
   visitor->trace(m_parentTreeScope);
   visitor->trace(m_idTargetObserverRegistry);
   visitor->trace(m_selection);
   visitor->trace(m_elementsById);
   visitor->trace(m_imageMapsByName);
   visitor->trace(m_scopedStyleResolver);
   visitor->trace(m_radioButtonGroupScope);
 }
 
 }  // namespace blink