Use float for scroll offset.

third_party/WebKit/Source/core/layout/LayoutBox.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007 Apple Inc. 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
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 529 matching lines @@
   // scrolling).
   virtual LayoutUnit scrollLeft() const;
   virtual LayoutUnit scrollTop() const;
   virtual LayoutUnit scrollWidth() const;
   virtual LayoutUnit scrollHeight() const;
   int pixelSnappedScrollWidth() const;
   int pixelSnappedScrollHeight() const;
   virtual void setScrollLeft(LayoutUnit);
   virtual void setScrollTop(LayoutUnit);
 
-  void scrollToOffset(const DoubleSize&,
-                      ScrollBehavior = ScrollBehaviorInstant);
-  void scrollByRecursively(const DoubleSize& delta);
+  void scrollToPosition(const FloatPoint&,

[bokan, 2016/10/02 19:47:51]

Why FloatPoint instead of ScrollOffset?

[szager1, 2016/10/05 07:43:36]

The convention I'm using is:

'position' is a point in the coordinate system of the overflow rect.
'offset' is a distance from the scroll origin.

Using a Point type is intuitive for something called 'position', and it also
helps prevent (via static type checking) inadvertently using the wrong quantity
in code.

[bokan, 2016/10/06 22:32:17]

Acknowledged.

+                        ScrollBehavior = ScrollBehaviorInstant);
+  void scrollByRecursively(const ScrollOffset& delta);
   // If makeVisibleInVisualViewport is set, the visual viewport will be scrolled
   // if required to make the rect visible.
   void scrollRectToVisible(const LayoutRect&,
                            const ScrollAlignment& alignX,
                            const ScrollAlignment& alignY,
                            ScrollType = ProgrammaticScroll,
                            bool makeVisibleInVisualViewport = true);
 
   LayoutRectOutsets marginBoxOutsets() const override {
     return m_marginBoxOutsets;
@@ skipping 1013 matching lines @@
 
 inline bool LayoutBox::isForcedFragmentainerBreakValue(EBreak breakValue) {
   return breakValue == BreakColumn || breakValue == BreakLeft ||
          breakValue == BreakPage || breakValue == BreakRecto ||
          breakValue == BreakRight || breakValue == BreakVerso;
 }
 
 }  // namespace blink
 
 #endif  // LayoutBox_h