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

Source/core/layout/LayoutImage.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011-2012. All rights reserved.
  *
@@ skipping 44 matching lines @@
     : LayoutReplaced(element, LayoutSize())
     , m_didIncrementVisuallyNonEmptyPixelCount(false)
     , m_isGeneratedContent(false)
     , m_imageDevicePixelRatio(1.0f)
 {
     ResourceLoadPriorityOptimizer::resourceLoadPriorityOptimizer()->addLayoutObject(this);
 }
 
 LayoutImage* LayoutImage::createAnonymous(Document* document)
 {
-    LayoutImage* image = new LayoutImage(0);
+    LayoutImage* image = new LayoutImage(nullptr);
     image->setDocumentForAnonymous(document);
     return image;
 }
 
 LayoutImage::~LayoutImage()
 {
 }
 
 void LayoutImage::willBeDestroyed()
 {
@@ skipping 267 matching lines @@
 bool LayoutImage::needsPreferredWidthsRecalculation() const
 {
     if (LayoutReplaced::needsPreferredWidthsRecalculation())
         return true;
     return embeddedContentBox();
 }
 
 LayoutBox* LayoutImage::embeddedContentBox() const
 {
     if (!m_imageResource)
-        return 0;
+        return nullptr;
 
     ImageResource* cachedImage = m_imageResource->cachedImage();
     if (cachedImage && cachedImage->image() && cachedImage->image()->isSVGImage())
         return toSVGImage(cachedImage->image())->embeddedContentBox();
 
-    return 0;
+    return nullptr;
 }
 
 } // namespace blink