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

Source/core/layout/BidiRunForLine.cpp

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc.
  * All right reserved.
  * Copyright (C) 2010 Google 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 16 matching lines @@
 #include "config.h"
 #include "core/layout/BidiRunForLine.h"
 
 #include "core/layout/line/InlineIterator.h"
 
 namespace blink {
 
 using namespace WTF::Unicode;
 
 static LayoutObject* firstLayoutObjectForDirectionalityDetermination(
-    LayoutObject* root, LayoutObject* current = 0)
+    LayoutObject* root, LayoutObject* current = nullptr)
 {
     LayoutObject* next = current;
     while (current) {
         if (isIsolated(current->style()->unicodeBidi())
             && (current->isLayoutInline() || current->isLayoutBlock())) {
             if (current != root)
-                current = 0;
+                current = nullptr;
             else
                 current = next;
             break;
         }
         current = current->parent();
     }
 
     if (!current)
         current = root->slowFirstChild();
 
     while (current) {
-        next = 0;
+        next = nullptr;
         if (isIteratorTarget(current) && !(current->isText()
             && toLayoutText(current)->isAllCollapsibleWhitespace()))
             break;
 
         if (!isIteratorTarget(current)
             && !isIsolated(current->style()->unicodeBidi()))
             next = current->slowFirstChild();
 
         if (!next) {
             while (current && current != root) {
@@ skipping 139 matching lines @@
                 isolatedResolver.isolatedRuns());
             currentRoot = isolatedInline;
             restoreIsolatedMidpointStates(topResolver, isolatedResolver);
         }
     }
 }
 
 } // namespace blink
 
 #endif // BidiRunForLine_h