C++11: Replace 0 with nullptr where applicable in layout code.

Source/core/layout/LayoutTableCol.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, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 123 matching lines @@
 
     for (LayoutObject* child = firstChild(); child; child = child->nextSibling())
         child->clearPreferredLogicalWidthsDirty();
 }
 
 LayoutTable* LayoutTableCol::table() const
 {
     LayoutObject* table = parent();
     if (table && !table->isTable())
         table = table->parent();
-    return table && table->isTable() ? toLayoutTable(table) : 0;
+    return table && table->isTable() ? toLayoutTable(table) : nullptr;
 }
 
 LayoutTableCol* LayoutTableCol::enclosingColumnGroup() const
 {
     if (!parent()->isLayoutTableCol())
-        return 0;
+        return nullptr;
 
     LayoutTableCol* parentColumnGroup = toLayoutTableCol(parent());
     ASSERT(parentColumnGroup->isTableColumnGroup());
     ASSERT(isTableColumn());
     return parentColumnGroup;
 }
 
 LayoutTableCol* LayoutTableCol::nextColumn() const
 {
     // If |this| is a column-group, the next column is the colgroup's first child column.
@@ skipping 28 matching lines @@
     return style()->borderStart();
 }
 
 const BorderValue& LayoutTableCol::borderAdjoiningCellAfter(const LayoutTableCell* cell) const
 {
     ASSERT_UNUSED(cell, table()->colElement(cell->col() - 1) == this);
     return style()->borderEnd();
 }
 
 }