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

Source/core/layout/compositing/CompositingInputsUpdater.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CompositingInputsUpdater_h
 #define CompositingInputsUpdater_h
 
 #include "core/layout/LayoutGeometryMap.h"
 
 namespace blink {
@@ skipping 12 matching lines @@
 #endif
 
 private:
     enum UpdateType {
         DoNotForceUpdate,
         ForceUpdate,
     };
 
     struct AncestorInfo {
         AncestorInfo()
-            : ancestorStackingContext(0)
-            , enclosingCompositedLayer(0)
-            , lastScrollingAncestor(0)
+            : ancestorStackingContext(nullptr)
+            , enclosingCompositedLayer(nullptr)
+            , lastScrollingAncestor(nullptr)
             , hasAncestorWithClipOrOverflowClip(false)
             , hasAncestorWithClipPath(false)
         {
         }
 
         DeprecatedPaintLayer* ancestorStackingContext;
         DeprecatedPaintLayer* enclosingCompositedLayer;
         // Notice that lastScrollingAncestor isn't the same thing as
         // ancestorScrollingLayer. The former is just the nearest scrolling
         // along the DeprecatedPaintLayer::parent() chain. The latter is the layer that
         // actually controls the scrolling of this layer, which we find on the
         // containing block chain.
         DeprecatedPaintLayer* lastScrollingAncestor;
         bool hasAncestorWithClipOrOverflowClip;
         bool hasAncestorWithClipPath;
     };
 
     void updateRecursive(DeprecatedPaintLayer*, UpdateType, AncestorInfo);
 
     LayoutGeometryMap m_geometryMap;
     DeprecatedPaintLayer* m_rootLayer;
 };
 
 } // namespace blink
 
 #endif // CompositingInputsUpdater_h