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

Source/core/layout/svg/LayoutSVGResourceContainer.h

Index: Source/core/layout/svg/LayoutSVGResourceContainer.h
diff --git a/Source/core/layout/svg/LayoutSVGResourceContainer.h b/Source/core/layout/svg/LayoutSVGResourceContainer.h
index f03d9417f4ef86e318d8999f29b56d9751356e60..b0f7d7dd37fe65b1d31a7b03d5f3e6126bd10fbe 100644
--- a/Source/core/layout/svg/LayoutSVGResourceContainer.h
+++ b/Source/core/layout/svg/LayoutSVGResourceContainer.h
@@ -64,7 +64,7 @@ public:
     void addClientLayer(DeprecatedPaintLayer*);
     void removeClientLayer(DeprecatedPaintLayer*);
 
-    void invalidateCacheAndMarkForLayout(SubtreeLayoutScope* = 0);
+    void invalidateCacheAndMarkForLayout(SubtreeLayoutScope* = nullptr);
 
     static void markForLayoutAndParentResourceInvalidation(LayoutObject*, bool needsLayout = true);
 
@@ -110,12 +110,12 @@ private:
 inline LayoutSVGResourceContainer* getLayoutSVGResourceContainerById(TreeScope& treeScope, const AtomicString& id)
 {
     if (id.isEmpty())
-        return 0;
+        return nullptr;
 
     if (LayoutSVGResourceContainer* layoutResource = treeScope.document().accessSVGExtensions().resourceById(id))
         return layoutResource;
 
-    return 0;
+    return nullptr;
 }
 
 template<typename Layout>
@@ -125,7 +125,7 @@ Layout* getLayoutSVGResourceById(TreeScope& treeScope, const AtomicString& id)
         if (container->resourceType() == Layout::s_resourceType)
             return static_cast<Layout*>(container);
     }
-    return 0;
+    return nullptr;
 }
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutSVGResourceContainer, isSVGResourceContainer());