LayoutTable: gracefully degrade in the presence of collspan > 1.

third_party/WebKit/Source/core/layout/LayoutTable.cpp

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 43 matching lines @@
 LayoutTable::LayoutTable(Element* element)
     : LayoutBlock(element)
     , m_head(nullptr)
     , m_foot(nullptr)
     , m_firstBody(nullptr)
     , m_collapsedBordersValid(false)
     , m_hasColElements(false)
     , m_needsSectionRecalc(false)
     , m_columnLogicalWidthChanged(false)
     , m_columnLayoutObjectsValid(false)
-    , m_hasCellColspanThatDeterminesTableWidth(false)
+    , m_noCellColspanAtLeast(0)
     , m_hSpacing(0)
     , m_vSpacing(0)
     , m_borderStart(0)
     , m_borderEnd(0)
 {
     ASSERT(!childrenInline());
     m_effectiveColumnPositions.fill(0, 1);
 }
 
 LayoutTable::~LayoutTable()
@@ skipping 715 matching lines @@
     m_effectiveColumnPositions.grow(numEffectiveColumns() + 1);
 }
 
 void LayoutTable::appendEffectiveColumn(unsigned span)
 {
     unsigned newColumnIndex = m_effectiveColumns.size();
     m_effectiveColumns.append(span);
 
     // Unless the table has cell(s) with colspan that exceed the number of columns afforded
     // by the other rows in the table we can use the fast path when mapping columns to effective columns.
-    m_hasCellColspanThatDeterminesTableWidth = m_hasCellColspanThatDeterminesTableWidth || span > 1;
+    if (span == 1 && m_noCellColspanAtLeast + 1 == numEffectiveColumns()) {
+        m_noCellColspanAtLeast++;
+    }
 
     // Propagate the change in our columns representation to the sections that don't need
     // cell recalc. If they do, they will be synced up directly with m_columns later.
     for (LayoutObject* child = firstChild(); child; child = child->nextSibling()) {
         if (!child->isTableSection())
             continue;
 
         LayoutTableSection* section = toLayoutTableSection(child);
         if (section->needsCellRecalc())
             continue;
@@ skipping 67 matching lines @@
 }
 
 void LayoutTable::recalcSections() const
 {
     ASSERT(m_needsSectionRecalc);
 
     m_head = nullptr;
     m_foot = nullptr;
     m_firstBody = nullptr;
     m_hasColElements = false;
-    m_hasCellColspanThatDeterminesTableWidth = hasCellColspanThatDeterminesTableWidth();
+    m_noCellColspanAtLeast = calcNoCellColspanAtLeast();
 
     // We need to get valid pointers to caption, head, foot and first body again
     LayoutObject* nextSibling;
     for (LayoutObject* child = firstChild(); child; child = nextSibling) {
         nextSibling = child->nextSibling();
         switch (child->style()->display()) {
         case TABLE_COLUMN:
         case TABLE_COLUMN_GROUP:
             m_hasColElements = true;
             break;
@@ skipping 575 matching lines @@
 
 LayoutUnit LayoutTable::paddingRight() const
 {
     if (collapseBorders())
         return LayoutUnit();
 
     return LayoutBlock::paddingRight();
 }
 
 } // namespace blink