Move m_pageLogicalOffset from LayoutBlock to LayoutBoxRareData.

Source/core/layout/LayoutBox.h

Index: Source/core/layout/LayoutBox.h
diff --git a/Source/core/layout/LayoutBox.h b/Source/core/layout/LayoutBox.h
index 146126101f8070a095248e525f30b9300f03888f..82f7e9f942380f42a355da6fa57035936215623f 100644
--- a/Source/core/layout/LayoutBox.h
+++ b/Source/core/layout/LayoutBox.h
@@ -71,6 +71,8 @@ public:
 
     // Set by LayoutBox::updatePreviousBorderBoxSizeIfNeeded().
     LayoutSize m_previousBorderBoxSize;
+
+    LayoutUnit m_pageLogicalOffset;
 };
 
 class CORE_EXPORT LayoutBox : public LayoutBoxModelObject {
@@ -454,6 +456,11 @@ public:
 
     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);