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

Source/core/layout/LayoutFlexibleBox.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 66 matching lines @@
 {
     ASSERT(!childrenInline());
 }
 
 LayoutFlexibleBox::~LayoutFlexibleBox()
 {
 }
 
 LayoutFlexibleBox* LayoutFlexibleBox::createAnonymous(Document* document)
 {
-    LayoutFlexibleBox* layoutObject = new LayoutFlexibleBox(0);
+    LayoutFlexibleBox* layoutObject = new LayoutFlexibleBox(nullptr);
     layoutObject->setDocumentForAnonymous(document);
     return layoutObject;
 }
 
 void LayoutFlexibleBox::computeIntrinsicLogicalWidths(LayoutUnit& minLogicalWidth, LayoutUnit& maxLogicalWidth) const
 {
     // FIXME: We're ignoring flex-basis here and we shouldn't. We can't start honoring it though until
     // the flex shorthand stops setting it to 0.
     // See https://bugs.webkit.org/show_bug.cgi?id=116117 and http://crbug.com/240765.
     for (LayoutBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
@@ skipping 51 matching lines @@
     if (baseline == -1)
         baseline = synthesizedBaselineFromContentBox(*this, direction);
 
     return beforeMarginInLineDirection(direction) + baseline;
 }
 
 int LayoutFlexibleBox::firstLineBoxBaseline() const
 {
     if (isWritingModeRoot() || m_numberOfInFlowChildrenOnFirstLine <= 0)
         return -1;
-    LayoutBox* baselineChild = 0;
+    LayoutBox* baselineChild = nullptr;
     int childNumber = 0;
     for (LayoutBox* child = m_orderIterator.first(); child; child = m_orderIterator.next()) {
         if (child->isOutOfFlowPositioned())
             continue;
         if (alignmentForChild(*child) == ItemPositionBaseline && !hasAutoMarginsInCrossAxis(*child)) {
             baselineChild = child;
             break;
         }
         if (!baselineChild)
             baselineChild = child;
@@ skipping 1282 matching lines @@
             ASSERT(child);
             LayoutUnit lineCrossAxisExtent = lineContexts[lineNumber].crossAxisExtent;
             LayoutUnit originalOffset = lineContexts[lineNumber].crossAxisOffset - crossAxisStartEdge;
             LayoutUnit newOffset = contentExtent - originalOffset - lineCrossAxisExtent;
             adjustAlignmentForChild(*child, newOffset - originalOffset);
         }
     }
 }
 
 }