Use float for scroll offset.

third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 638 matching lines @@
 
 enum AcceleratedFixedRootBackgroundHistogramBuckets {
   ScrolledMainFrameBucket = 0,
   ScrolledMainFrameWithAcceleratedFixedRootBackground = 1,
   ScrolledMainFrameWithUnacceleratedFixedRootBackground = 2,
   AcceleratedFixedRootBackgroundHistogramMax = 3
 };
 
 void PaintLayerCompositor::frameViewDidScroll() {
   FrameView* frameView = m_layoutView.frameView();
-  IntPoint scrollPosition = frameView->scrollPosition();
+  IntSize scrollOffset = frameView->scrollOffsetInt();
 
   if (!m_scrollLayer)
     return;
 
   bool scrollingCoordinatorHandlesOffset = false;
   if (ScrollingCoordinator* scrollingCoordinator =
           this->scrollingCoordinator()) {
     scrollingCoordinatorHandlesOffset =
         scrollingCoordinator->scrollableAreaScrollLayerDidChange(frameView);
   }
 
   // Scroll position = scroll origin + scroll offset. Adjust the layer's
   // position to handle whatever the scroll coordinator isn't handling.
   // The scroll origin is non-zero for RTL pages with overflow.
   if (scrollingCoordinatorHandlesOffset)
     m_scrollLayer->setPosition(frameView->scrollOrigin());
   else
-    m_scrollLayer->setPosition(-scrollPosition);
+    m_scrollLayer->setPosition(IntPoint(-scrollOffset));
 
   DEFINE_STATIC_LOCAL(EnumerationHistogram, acceleratedBackgroundHistogram,
                       ("Renderer.AcceleratedFixedRootBackground",
                        AcceleratedFixedRootBackgroundHistogramMax));
   acceleratedBackgroundHistogram.count(ScrolledMainFrameBucket);
 }
 
 void PaintLayerCompositor::frameViewScrollbarsExistenceDidChange() {
   if (m_containerLayer)
     updateOverflowControlsLayers();
@@ skipping 658 matching lines @@
   } else if (graphicsLayer == m_scrollLayer.get()) {
     name = "Frame Scrolling Layer";
   } else {
     ASSERT_NOT_REACHED();
   }
 
   return name;
 }
 
 }  // namespace blink