Move LayoutObject to satellite NodeLayoutData that hangs from a Node.

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  *
@@ skipping 280 matching lines @@
 #if !defined(NDEBUG) || (defined(DUMP_NODE_STATISTICS) && DUMP_NODE_STATISTICS)
   TrackForDebugging();
 #endif
   InstanceCounters::IncrementNodeCounter();
 }
 
 Node::~Node() {
   // With Oilpan, the rare data finalizer also asserts for
   // this condition (we cannot directly access it here.)
   CHECK(HasRareData() || !GetLayoutObject());
+  if (!HasRareData() && !data_.node_layout_data_->IsSharedEmptyData())
+    delete data_.node_layout_data_;
   InstanceCounters::DecrementNodeCounter();
 }
 
 NodeRareData* Node::RareData() const {
   SECURITY_DCHECK(HasRareData());
   return static_cast<NodeRareData*>(data_.rare_data_);
 }
 
 NodeRareData& Node::EnsureRareData() {
   if (HasRareData())
     return *RareData();
 
   if (IsElementNode())
-    data_.rare_data_ = ElementRareData::Create(data_.layout_object_);
+    data_.rare_data_ = ElementRareData::Create(data_.node_layout_data_);
   else
-    data_.rare_data_ = NodeRareData::Create(data_.layout_object_);
+    data_.rare_data_ = NodeRareData::Create(data_.node_layout_data_);
 
   DCHECK(data_.rare_data_);
   SetFlag(kHasRareDataFlag);
   ScriptWrappableVisitor::WriteBarrier(this, RareData());
   return *RareData();
 }
 
 Node* Node::ToNode() {
   return this;
 }
@@ skipping 255 matching lines @@
       node = NodeTraversal::NextPostOrder(*node);
   }
 }
 
 LayoutBox* Node::GetLayoutBox() const {
   LayoutObject* layout_object = this->GetLayoutObject();
   return layout_object && layout_object->IsBox() ? ToLayoutBox(layout_object)
                                                  : nullptr;
 }
 
+void Node::SetLayoutObject(LayoutObject* layout_object) {

[esprehn, 2017/04/13 18:41:08]

This allocates a NodeLayoutData when setting a nullptr for layout_object, but
that's probably not what we want.

You could do something like:

NodeLayoutData* data = HasRareData() ? data_.rare_data_->GetNodeLayoutData() :
data_.node_layout_data_;
if (!data->IsSharedEmptyData()) {
  data->SetLayoutObject(layout_object);
  return;
}
if (!layout_object)
  return;
data = new NodeLayoutData(layout_object);
if (HasRareData()) {
  data_.rare_data_->SetNodeLayoutData(data);
} else {
  data_.node_layout_data_ = data;
}

[nainar, 2017/04/13 20:21:03]

Done. Also commented inline. 

+  if (HasRareData()) {
+    if (data_.rare_data_->GetNodeLayoutData()->IsSharedEmptyData())
+      data_.rare_data_->SetNodeLayoutData(new NodeLayoutData(layout_object));
+    else
+      data_.rare_data_->GetNodeLayoutData()->SetLayoutObject(layout_object);
+  } else {
+    if (data_.node_layout_data_->IsSharedEmptyData())
+      data_.node_layout_data_ = new NodeLayoutData(layout_object);
+    else
+      data_.node_layout_data_->SetLayoutObject(layout_object);
+  }
+}
+
 LayoutBoxModelObject* Node::GetLayoutBoxModelObject() const {
   LayoutObject* layout_object = this->GetLayoutObject();
   return layout_object && layout_object->IsBoxModelObject()
              ? ToLayoutBoxModelObject(layout_object)
              : nullptr;
 }
 
 LayoutRect Node::BoundingBox() const {
   if (GetLayoutObject())
     return LayoutRect(GetLayoutObject()->AbsoluteBoundingBoxRect());
@@ skipping 1938 matching lines @@
   if (node) {
     std::stringstream stream;
     node->PrintNodePathTo(stream);
     LOG(INFO) << stream.str();
   } else {
     LOG(INFO) << "Cannot showNodePath for <null>";
   }
 }
 
 #endif