Only allow forced fragmentainer breaks at class A break points.

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 303 matching lines @@
     void determineLogicalLeftPositionForChild(LayoutBox& child);
 
     PaintInvalidationReason invalidatePaintIfNeeded(const PaintInvalidationState&) 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, BlockChildrenLayoutInfo&);
+
+    // Handle breaking policy before the child, and insert a forced break in front of it if needed.
+    // Returns true if a forced break was inserted.
+    bool insertForcedBreakBeforeChildIfNeeded(LayoutBox& child, BlockChildrenLayoutInfo&);
+
     void layoutBlockChild(LayoutBox& child, BlockChildrenLayoutInfo&);
-    void adjustPositionedBlock(LayoutBox& child, const MarginInfo&);
+    void adjustPositionedBlock(LayoutBox& child, const BlockChildrenLayoutInfo&);
     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);
 
     bool hasOverhangingFloats() { return parent() && containsFloats() && lowestFloatLogicalBottom() > logicalHeight(); }
@@ skipping 101 matching lines @@
     };
     MarginValues marginValuesForChild(LayoutBox& child) const;
 
     // Allocated only when some of these fields have non-default values
     struct LayoutBlockFlowRareData {
         WTF_MAKE_NONCOPYABLE(LayoutBlockFlowRareData); USING_FAST_MALLOC(LayoutBlockFlowRareData);
     public:
         LayoutBlockFlowRareData(const LayoutBlockFlow* block)
             : m_margins(positiveMarginBeforeDefault(block), negativeMarginBeforeDefault(block), positiveMarginAfterDefault(block), negativeMarginAfterDefault(block))
             , m_multiColumnFlowThread(nullptr)
+            , m_breakBefore(BreakAuto)
+            , m_breakAfter(BreakAuto)
             , m_lineBreakToAvoidWidow(-1)
             , m_didBreakAtLineToAvoidWidow(false)
             , m_discardMarginBefore(false)
             , m_discardMarginAfter(false)
         {
         }
 
         static LayoutUnit positiveMarginBeforeDefault(const LayoutBlockFlow* block)
         {
             return block->marginBefore().clampNegativeToZero();
         }
         static LayoutUnit negativeMarginBeforeDefault(const LayoutBlockFlow* block)
         {
             return (-block->marginBefore()).clampNegativeToZero();
         }
         static LayoutUnit positiveMarginAfterDefault(const LayoutBlockFlow* block)
         {
             return block->marginAfter().clampNegativeToZero();
         }
         static LayoutUnit negativeMarginAfterDefault(const LayoutBlockFlow* block)
         {
             return (-block->marginAfter()).clampNegativeToZero();
         }
 
         MarginValues m_margins;
         LayoutUnit m_paginationStrutPropagatedFromChild;
 
         LayoutMultiColumnFlowThread* m_multiColumnFlowThread;
 
+        unsigned m_breakBefore : 4;
+        unsigned m_breakAfter : 4;
         int m_lineBreakToAvoidWidow;
         bool m_didBreakAtLineToAvoidWidow : 1;
         bool m_discardMarginBefore : 1;
         bool m_discardMarginAfter : 1;
     };
 
     const FloatingObjects* floatingObjects() const { return m_floatingObjects.get(); }
 
     static void setAncestorShouldPaintFloatingObject(const LayoutBox& floatBox, bool shouldPaint);
 
@@ skipping 33 matching lines @@
 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);
+    LayoutUnit estimateLogicalTopPosition(LayoutBox& child, const BlockChildrenLayoutInfo&, 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.
+    // Apply any forced fragmentainer break that's set on the current class A break point.
+    LayoutUnit applyForcedBreak(LayoutUnit logicalOffset, EBreak);
+
+    void setBreakBefore(EBreak);
+    void setBreakAfter(EBreak);
+    EBreak breakBefore() const override;
+    EBreak breakAfter() const override;
 
     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;
 
@@ skipping 47 matching lines @@
 
 // END METHODS DEFINED IN LayoutBlockFlowLine
 
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutBlockFlow, isLayoutBlockFlow());
 
 } // namespace blink
 
 #endif // LayoutBlockFlow_h