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

Source/core/layout/LayoutScrollbarPart.cpp

 /*
  * Copyright (C) 2008 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 17 matching lines @@
 
 #include "core/frame/UseCounter.h"
 #include "core/layout/LayoutScrollbar.h"
 #include "core/layout/LayoutScrollbarTheme.h"
 #include "core/layout/LayoutView.h"
 #include "platform/LengthFunctions.h"
 
 namespace blink {
 
 LayoutScrollbarPart::LayoutScrollbarPart(LayoutScrollbar* scrollbar, ScrollbarPart part)
-    : LayoutBlock(0)
+    : LayoutBlock(nullptr)
     , m_scrollbar(scrollbar)
     , m_part(part)
 {
 }
 
 LayoutScrollbarPart::~LayoutScrollbarPart()
 {
 }
 
 static void recordScrollbarPartStats(Document& document, ScrollbarPart part)
@@ skipping 144 matching lines @@
                 return;
             }
         }
 
         LayoutBlock::imageChanged(image, rect);
     }
 }
 
 LayoutObject* LayoutScrollbarPart::layoutObjectOwningScrollbar() const
 {
-    if (!m_scrollbar)
-        return 0;
-    return m_scrollbar->owningLayoutObject();
+    return (!m_scrollbar) ? nullptr : m_scrollbar->owningLayoutObject();
 }
 
 }