Optimize RenderTable::colToEffCol() for tables without colspans

Source/core/rendering/RenderTable.h

 /*
  * 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, 2009, 2010 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
@@ skipping 153 matching lines @@
 
     unsigned lastColumnIndex() const { return numEffCols() - 1; }
 
     void splitColumn(unsigned position, unsigned firstSpan);
     void appendColumn(unsigned span);
     unsigned numEffCols() const { return m_columns.size(); }
     unsigned spanOfEffCol(unsigned effCol) const { return m_columns[effCol].span; }
 
     unsigned colToEffCol(unsigned column) const
     {
+        if (!m_hasCellColspanThatDeterminesTableWidth)
+            return column;
+
         unsigned effColumn = 0;
         unsigned numColumns = numEffCols();
         for (unsigned c = 0; effColumn < numColumns && c + m_columns[effColumn].span - 1 < column; ++effColumn)
             c += m_columns[effColumn].span;
         return effColumn;
     }
 
     unsigned effColToCol(unsigned effCol) const
     {
+        if (!m_hasCellColspanThatDeterminesTableWidth)
+            return effCol;
+
         unsigned c = 0;
         for (unsigned i = 0; i < effCol; i++)
             c += m_columns[i].span;
         return c;
     }
 
     LayoutUnit borderSpacingInRowDirection() const
     {
         if (unsigned effectiveColumnCount = numEffCols())
             return static_cast<LayoutUnit>(effectiveColumnCount + 1) * hBorderSpacing();
@@ skipping 132 matching lines @@
 
     CollapsedBorderValues m_collapsedBorders;
     const CollapsedBorderValue* m_currentBorder;
     bool m_collapsedBordersValid : 1;
 
     mutable bool m_hasColElements : 1;
     mutable bool m_needsSectionRecalc : 1;
 
     bool m_columnLogicalWidthChanged : 1;
     mutable bool m_columnRenderersValid: 1;
+    mutable bool m_hasCellColspanThatDeterminesTableWidth : 1;
+    bool hasCellColspanThatDeterminesTableWidth() const
+    {
+        for (unsigned c = 0; c < numEffCols(); c++) {
+            if (m_columns[c].span > 1)
+                return true;
+        }
+        return false;
+    }
 
     short m_hSpacing;
     short m_vSpacing;
     int m_borderStart;
     int m_borderEnd;
 };
 
 inline RenderTableSection* RenderTable::topSection() const
 {
     ASSERT(!needsSectionRecalc());
     if (m_head)
         return m_head;
     if (m_firstBody)
         return m_firstBody;
     return m_foot;
 }
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderTable, isTable());
 
 } // namespace WebCore
 
 #endif // RenderTable_h