Move m_pageLogicalOffset from LayoutBlock to LayoutBoxRareData.

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 53 matching lines @@
     InlineBox* m_inlineBoxWrapper;
 
     // For spanners, the spanner placeholder that lays us out within the multicol container.
     LayoutMultiColumnSpannerPlaceholder* m_spannerPlaceholder;
 
     LayoutUnit m_overrideLogicalContentHeight;
     LayoutUnit m_overrideLogicalContentWidth;
 
     // Set by LayoutBox::updatePreviousBorderBoxSizeIfNeeded().
     LayoutSize m_previousBorderBoxSize;
+
+    LayoutUnit m_pageLogicalOffset;
 };
 
 class CORE_EXPORT LayoutBox : public LayoutBoxModelObject {
 public:
     explicit LayoutBox(ContainerNode*);
 
     virtual DeprecatedPaintLayerType layerTypeRequired() const override;
 
     virtual bool backgroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect) const override;
 
@@ skipping 363 matching lines @@
     };
     // Resolve auto margins in the chosen direction of the containing block so that objects can be pushed to the start, middle or end
     // of the containing block.
     void computeMarginsForDirection(MarginDirection forDirection, const LayoutBlock* containingBlock, LayoutUnit containerWidth, LayoutUnit childWidth, LayoutUnit& marginStart, LayoutUnit& marginEnd, Length marginStartLength, Length marginStartEnd) const;
 
     // Used to resolve margins in the containing block's block-flow direction.
     void computeAndSetBlockDirectionMargins(const LayoutBlock* containingBlock);
 
     virtual LayoutUnit offsetFromLogicalTopOfFirstPage() const;
 
+    // The page logical offset is the object's offset from the top of the page in the page progression
+    // direction (so an x-offset in vertical text and a y-offset for horizontal text).

[leviw_travelin_and_unemployed, 2015/05/20 21:23:44]

Mega-Nit-feel-free-to-ignore: I may describe the common case first (horizontal
text).

[mstensho (USE GERRIT), 2015/05/20 21:47:32]

That would have been better, but since I just moved this comment from the other
place, I'll leave it alone for now.

+    LayoutUnit pageLogicalOffset() const { return m_rareData ? m_rareData->m_pageLogicalOffset : LayoutUnit(); }
+    void setPageLogicalOffset(LayoutUnit);
+
     void positionLineBox(InlineBox*);
     void moveWithEdgeOfInlineContainerIfNecessary(bool isHorizontal);
     void markStaticPositionedBoxForLayout(bool isHorizontal, bool isInline);
 
     virtual InlineBox* createInlineBox();
     void dirtyLineBoxes(bool fullLayout);
 
     // For inline replaced elements, this function returns the inline box that owns us.  Enables
     // the replaced LayoutObject to quickly determine what line it is contained on and to easily
     // iterate over structures on the line.
@@ skipping 462 matching lines @@
         if (UNLIKELY(inlineBoxWrapper() != 0))
             deleteLineBoxWrapper();
     }
 
     ensureRareData().m_inlineBoxWrapper = boxWrapper;
 }
 
 } // namespace blink
 
 #endif // LayoutBox_h