Move LayoutObject to satellite NodeLayoutData that hangs from a Node.

third_party/WebKit/Source/core/dom/Node.h

Index: third_party/WebKit/Source/core/dom/Node.h
diff --git a/third_party/WebKit/Source/core/dom/Node.h b/third_party/WebKit/Source/core/dom/Node.h
index d0ee8a6e2523a6946908c339f58cf6fc054cf7c1..8dba95a0da8eb79541b3a04a853740c5f27cc285 100644
--- a/third_party/WebKit/Source/core/dom/Node.h
+++ b/third_party/WebKit/Source/core/dom/Node.h
@@ -97,23 +97,21 @@ enum class SlotChangeType {
   kChained,
 };
 
-class NodeRareDataBase {
+class NodeLayoutData {
  public:
+  explicit NodeLayoutData(LayoutObject* layout_object) : layout_object_(layout_object) {}
   LayoutObject* GetLayoutObject() const { return layout_object_; }
   void SetLayoutObject(LayoutObject* layout_object) {
     layout_object_ = layout_object;
   }
 
- protected:
-  NodeRareDataBase(LayoutObject* layout_object)
-      : layout_object_(layout_object) {}
-
- protected:
-  // LayoutObjects are fully owned by their DOM node. See LayoutObject's
-  // LIFETIME documentation section.
+ private:
   LayoutObject* layout_object_;
 };
 
+class NodeRareDataBase {
+};
+
 class Node;
 WILL_NOT_BE_EAGERLY_TRACED_CLASS(Node);
 
@@ -563,14 +561,10 @@ class CORE_EXPORT Node : public EventTarget {
   // Note that if a Node has a layoutObject, it's parentNode is guaranteed to
   // have one as well.
   LayoutObject* GetLayoutObject() const {
-    return HasRareData() ? data_.rare_data_->GetLayoutObject()
-                         : data_.layout_object_;
+    return data_.node_layout_data_ ? data_.node_layout_data_->GetLayoutObject() : nullptr;
   }
   void SetLayoutObject(LayoutObject* layout_object) {
-    if (HasRareData())
-      data_.rare_data_->SetLayoutObject(layout_object);
-    else
-      data_.layout_object_ = layout_object;
+    data_.node_layout_data_->SetLayoutObject(layout_object);
   }
 
   // Use these two methods with caution.
@@ -925,10 +919,10 @@ class CORE_EXPORT Node : public EventTarget {
   Member<Node> next_;
   // When a node has rare data we move the layoutObject into the rare data.
   union DataUnion {
-    DataUnion() : layout_object_(nullptr) {}
+    DataUnion() : node_layout_data_(nullptr) {}
     // LayoutObjects are fully owned by their DOM node. See LayoutObject's
     // LIFETIME documentation section.
-    LayoutObject* layout_object_;
+    NodeLayoutData* node_layout_data_;

[nainar, 2017/04/11 06:03:59]

If the DataUnion is a NodeLayoutData we then have a LayoutObject stored on the
Node through this NodeLayoutData

     NodeRareDataBase* rare_data_;

[nainar, 2017/04/11 06:03:59]

However, if we have a NodeRareDataBase we don't have a LayoutObject? 

This seems wrong. 

I think we will have to retain storing the LayoutObject on NodeRareDataBase. 

Either directly or via an instance of NodeLayoutData.

   } data_;
 };