Only honor break-* values when appropriate.

third_party/WebKit/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 602 matching lines @@
     // Pagination struts are either set in front of a block-level box (here) or before a line
     // (RootInlineBox::paginationStrut()).
     LayoutUnit paginationStrut() const { return m_rareData ? m_rareData->m_paginationStrut : LayoutUnit(); }
     void setPaginationStrut(LayoutUnit);
     void resetPaginationStrut()
     {
         if (m_rareData)
             m_rareData->m_paginationStrut = LayoutUnit();
     }
 
+    // Is the specified break-before or break-after value supported on this object? It needs to be
+    // in-flow all the way up to a fragmentation context that supports the specified value.
+    bool isBreakBetweenControllable(EBreak) const;
+
+    // Is the specified break-inside value supported on this object? It needs to be contained by a
+    // fragmentation context that supports the specified value.
+    bool isBreakInsideControllable(EBreak) const;
+
+    EBreak breakAfter() const;
+    EBreak breakBefore() const;
+    EBreak breakInside() const;
+
+    static bool isForcedFragmentainerBreakValue(EBreak);
+
     bool hasForcedBreakBefore() const;
     bool hasForcedBreakAfter() const;
 
     LayoutRect clippedOverflowRectForPaintInvalidation(const LayoutBoxModelObject* paintInvalidationContainer, const PaintInvalidationState* = nullptr) const override;
     void mapToVisibleRectInAncestorSpace(const LayoutBoxModelObject* ancestor, LayoutRect&, const PaintInvalidationState*) const override;
     virtual void invalidatePaintForOverhangingFloats(bool paintAllDescendants);
 
     LayoutUnit containingBlockLogicalHeightForGetComputedStyle() const;
 
     LayoutUnit containingBlockLogicalWidthForContent() const override;
@@ skipping 495 matching lines @@
         // Otherwise, there will two line box wrappers keeping the reference to this layoutObject, and
         // only one will be notified when the layoutObject is getting destroyed. The second line box wrapper
         // will keep a stale reference.
         if (UNLIKELY(m_inlineBoxWrapper != nullptr))
             deleteLineBoxWrapper();
     }
 
     m_inlineBoxWrapper = boxWrapper;
 }
 
+inline bool LayoutBox::isForcedFragmentainerBreakValue(EBreak breakValue)
+{
+    return breakValue == BreakColumn
+        || breakValue == BreakLeft
+        || breakValue == BreakPage
+        || breakValue == BreakRecto
+        || breakValue == BreakRight
+        || breakValue == BreakVerso;
+}
+
 } // namespace blink
 
 #endif // LayoutBox_h