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

Source/core/layout/compositing/CompositingLayerAssigner.cpp

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2014 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:
  * 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
@@ skipping 192 matching lines @@
 
         // Issue a paint invalidation, since |layer| may have been added to an already-existing squashing layer.
         TRACE_LAYER_INVALIDATION(layer, InspectorLayerInvalidationTrackingEvent::AddedToSquashingLayer);
         layersNeedingPaintInvalidation.append(layer);
         m_layersChanged = true;
     } else if (compositedLayerUpdate == RemoveFromSquashingLayer) {
         if (layer->groupedMapping()) {
             // Before removing |layer| from an already-existing squashing layer that may have other content, issue a paint invalidation.
             m_compositor->paintInvalidationOnCompositingChange(layer);
             layer->groupedMapping()->setNeedsGraphicsLayerUpdate(GraphicsLayerUpdateSubtree);
-            layer->setGroupedMapping(0);
+            layer->setGroupedMapping(nullptr);
         }
 
         // If we need to issue paint invalidations, do so now that we've removed it from a squashed layer.
         TRACE_LAYER_INVALIDATION(layer, InspectorLayerInvalidationTrackingEvent::RemovedFromSquashingLayer);
         layersNeedingPaintInvalidation.append(layer);
         m_layersChanged = true;
 
         layer->setLostGroupedMapping(false);
     }
 }
@@ skipping 10 matching lines @@
     m_compositor->updateDirectCompositingReasons(reflectionLayer);
 
     // FIXME: Why do we updateGraphicsLayerConfiguration here instead of in the GraphicsLayerUpdater?
     if (reflectionLayer->hasCompositedDeprecatedPaintLayerMapping())
         reflectionLayer->compositedDeprecatedPaintLayerMapping()->updateGraphicsLayerConfiguration();
 }
 
 static ScrollingCoordinator* scrollingCoordinatorFromLayer(DeprecatedPaintLayer& layer)
 {
     Page* page = layer.layoutObject()->frame()->page();
-    if (!page)
-        return 0;
-
-    return page->scrollingCoordinator();
+    return (!page) ? nullptr : page->scrollingCoordinator();
 }
 
 void CompositingLayerAssigner::assignLayersToBackingsInternal(DeprecatedPaintLayer* layer, SquashingState& squashingState, Vector<DeprecatedPaintLayer*>& layersNeedingPaintInvalidation)
 {
     if (requiresSquashing(layer->compositingReasons())) {
         CompositingReasons reasonsPreventingSquashing = getReasonsPreventingSquashing(layer, squashingState);
         if (reasonsPreventingSquashing)
             layer->setCompositingReasons(layer->compositingReasons() | reasonsPreventingSquashing);
     }
 
@@ skipping 33 matching lines @@
     // At this point, if the layer is to be separately composited, then its backing becomes the most recent in paint-order.
     if (layer->compositingState() == PaintsIntoOwnBacking) {
         ASSERT(!requiresSquashing(layer->compositingReasons()));
         squashingState.updateSquashingStateForNewMapping(layer->compositedDeprecatedPaintLayerMapping(), layer->hasCompositedDeprecatedPaintLayerMapping());
     }
 
     if (layer->scrollParent())
         layer->scrollParent()->scrollableArea()->setTopmostScrollChild(layer);
 
     if (layer->needsCompositedScrolling())
-        layer->scrollableArea()->setTopmostScrollChild(0);
+        layer->scrollableArea()->setTopmostScrollChild(nullptr);
 
     DeprecatedPaintLayerStackingNodeIterator iterator(*layer->stackingNode(), NormalFlowChildren | PositiveZOrderChildren);
     while (DeprecatedPaintLayerStackingNode* curNode = iterator.next())
         assignLayersToBackingsInternal(curNode->layer(), squashingState, layersNeedingPaintInvalidation);
 
     if (squashingState.hasMostRecentMapping && &squashingState.mostRecentMapping->owningLayer() == layer)
         squashingState.haveAssignedBackingsToEntireSquashingLayerSubtree = true;
 }
 
 }