Add marginBeforeIfFloating() to LayoutBlockFlow.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003-2013 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
@@ skipping 498 matching lines @@
             m_rareData->m_discardMarginBefore = false;
             m_rareData->m_discardMarginAfter = false;
         }
     }
 
     virtual ETextAlign textAlignmentForLine(bool endsWithSoftBreak) const;
 private:
     LayoutUnit collapsedMarginBefore() const final { return maxPositiveMarginBefore() - maxNegativeMarginBefore(); }
     LayoutUnit collapsedMarginAfter() const final { return maxPositiveMarginAfter() - maxNegativeMarginAfter(); }
 
+    // Floats' margins do not collapse with page or column boundaries, and we therefore need to
+    // treat them specially in some cases.
+    LayoutUnit marginBeforeIfFloating() const { return isFloating() ? marginBefore() : LayoutUnit(); }
+
     LayoutUnit collapseMargins(LayoutBox& child, MarginInfo&, bool childIsSelfCollapsing, bool childDiscardMarginBefore, bool childDiscardMarginAfter);
     LayoutUnit clearFloatsIfNeeded(LayoutBox& child, MarginInfo&, LayoutUnit oldTopPosMargin, LayoutUnit oldTopNegMargin, LayoutUnit yPos, bool childIsSelfCollapsing, bool childDiscardMargin);
     LayoutUnit estimateLogicalTopPosition(LayoutBox& child, const MarginInfo&, LayoutUnit& estimateWithoutPagination);
     void marginBeforeEstimateForChild(LayoutBox&, LayoutUnit&, LayoutUnit&, bool&) const;
     void handleAfterSideOfBlock(LayoutBox* lastChild, LayoutUnit top, LayoutUnit bottom, MarginInfo&);
     void setCollapsedBottomMargin(const MarginInfo&);
 
     LayoutUnit applyBeforeBreak(LayoutBox& child, LayoutUnit logicalOffset); // If the child has a before break, then return a new yPos that shifts to the top of the next page/column.
     LayoutUnit applyAfterBreak(LayoutBox& child, LayoutUnit logicalOffset, MarginInfo&); // If the child has an after break, then return a new offset that shifts to the top of the next page/column.
 
@@ skipping 56 matching lines @@
 
 // END METHODS DEFINED IN LayoutBlockFlowLine
 
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutBlockFlow, isLayoutBlockFlow());
 
 } // namespace blink
 
 #endif // LayoutBlockFlow_h