Class A fragmentainer break points also exist between zero-height blocks.

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 26 matching lines @@
 #define LayoutBlockFlow_h
 
 #include "core/CoreExport.h"
 #include "core/layout/FloatingObjects.h"
 #include "core/layout/LayoutBlock.h"
 #include "core/layout/line/TrailingObjects.h"
 #include "core/style/ComputedStyleConstants.h"
 
 namespace blink {
 
+class BlockChildrenLayoutInfo;
 class ClipScope;
 class MarginInfo;
 class LineBreaker;
 class LineInfo;
 class LineWidth;
 class LayoutMultiColumnFlowThread;
 class LayoutMultiColumnSpannerPlaceholder;
 class LayoutRubyRun;
 template <class Run> class BidiRunList;
 
@@ skipping 255 matching lines @@
     void setLogicalTopForChild(LayoutBox& child, LayoutUnit logicalTop);
     void determineLogicalLeftPositionForChild(LayoutBox& child);
 
     PaintInvalidationReason invalidatePaintIfNeeded(PaintInvalidationState&, const LayoutBoxModelObject& paintInvalidationContainer) override;
 
 private:
     bool layoutBlockFlow(bool relayoutChildren, LayoutUnit& pageLogicalHeight, SubtreeLayoutScope&);
     void layoutBlockChildren(bool relayoutChildren, SubtreeLayoutScope&, LayoutUnit beforeEdge, LayoutUnit afterEdge);
 
     void markDescendantsWithFloatsForLayoutIfNeeded(LayoutBlockFlow& child, LayoutUnit newLogicalTop, LayoutUnit previousFloatLogicalBottom);
-    bool positionAndLayoutOnceIfNeeded(LayoutBox& child, LayoutUnit newLogicalTop, LayoutUnit& previousFloatLogicalBottom);
-    void layoutBlockChild(LayoutBox& child, MarginInfo&, LayoutUnit& previousFloatLogicalBottom);
+    bool positionAndLayoutOnceIfNeeded(LayoutBox& child, LayoutUnit newLogicalTop, BlockChildrenLayoutInfo&);
+    void layoutBlockChild(LayoutBox& child, BlockChildrenLayoutInfo&);
     void adjustPositionedBlock(LayoutBox& child, const MarginInfo&);
     void adjustFloatingBlock(const MarginInfo&);
 
     LayoutPoint computeLogicalLocationForFloat(const FloatingObject&, LayoutUnit logicalTopOffset) const;
 
     void removeFloatingObject(LayoutBox*);
     void removeFloatingObjectsBelow(FloatingObject*, int logicalOffset);
 
     LayoutUnit getClearDelta(LayoutBox* child, LayoutUnit yPos);
 
@@ skipping 192 matching lines @@
     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.
 
-    LayoutUnit adjustBlockChildForPagination(LayoutUnit logicalTop, LayoutBox& child, bool atBeforeSideOfBlock);
+    LayoutUnit adjustBlockChildForPagination(LayoutUnit logicalTop, LayoutBox& child, BlockChildrenLayoutInfo&, bool atBeforeSideOfBlock);
     // Computes a deltaOffset value that put a line at the top of the next page if it doesn't fit on the current page.
     void adjustLinePositionForPagination(RootInlineBox&, LayoutUnit& deltaOffset);
     // If the child is unsplittable and can't fit on the current page, return the top of the next page/column.
     LayoutUnit adjustForUnsplittableChild(LayoutBox&, LayoutUnit logicalOffset) const;
 
     // Used to store state between styleWillChange and styleDidChange
     static bool s_canPropagateFloatIntoSibling;
 
     LayoutBlockFlowRareData& ensureRareData();
 
@@ skipping 45 matching lines @@
 
 // END METHODS DEFINED IN LayoutBlockFlowLine
 
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutBlockFlow, isLayoutBlockFlow());
 
 } // namespace blink
 
 #endif // LayoutBlockFlow_h