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

Source/core/layout/ImageQualityController.cpp

 /*
  * Copyright (C) 2013 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 21 matching lines @@
 #include "core/layout/ImageQualityController.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "platform/graphics/GraphicsContext.h"
 
 namespace blink {
 
 static const double cLowQualityTimeThreshold = 0.500; // 500 ms
 
-static ImageQualityController* gImageQualityController = 0;
+static ImageQualityController* gImageQualityController = nullptr;
 
 ImageQualityController* ImageQualityController::imageQualityController()
 {
     if (!gImageQualityController)
         gImageQualityController = new ImageQualityController;
 
     return gImageQualityController;
 }
 
 void ImageQualityController::remove(LayoutObject* layoutObject)
 {
     if (gImageQualityController) {
         gImageQualityController->objectDestroyed(layoutObject);
         if (gImageQualityController->isEmpty()) {
             delete gImageQualityController;
-            gImageQualityController = 0;
+            gImageQualityController = nullptr;
         }
     }
 }
 
 bool ImageQualityController::has(LayoutObject* layoutObject)
 {
     return gImageQualityController && gImageQualityController->m_objectLayerSizeMap.contains(layoutObject);
 }
 
 InterpolationQuality ImageQualityController::chooseInterpolationQuality(GraphicsContext* context, LayoutObject* object, Image* image, const void* layer, const LayoutSize& layoutSize)
@@ skipping 159 matching lines @@
     // This object has been resized to two different sizes while the timer
     // is active, so draw at low quality, set the flag for animated resizes and
     // the object to the list for high quality redraw.
     set(object, innerMap, layer, layoutSize);
     m_animatedResizeIsActive = true;
     restartTimer();
     return true;
 }
 
 } // namespace blink