Move LayoutObject to satellite NodeLayoutData that hangs from a Node.

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

 /*
  * Copyright (C) 2012 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 59 matching lines @@
   else
     TraceWrappersAfterDispatch(visitor);
 }
 
 DEFINE_TRACE_WRAPPERS_AFTER_DISPATCH(NodeRareData) {
   visitor->TraceWrappersWithManualWriteBarrier(node_lists_);
   visitor->TraceWrappersWithManualWriteBarrier(mutation_observer_data_);
 }
 
 void NodeRareData::FinalizeGarbageCollectedObject() {
-  CHECK(!GetLayoutObject());
+  CHECK(!GetNodeLayoutData()->GetLayoutObject());

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

Can we put this in the destructor of NodeLayoutData instead?

~NodeLayoutData() {
  CHECK(!layout_object_);
}

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

Done. 

   if (is_element_rare_data_)
     static_cast<ElementRareData*>(this)->~ElementRareData();
   else
     this->~NodeRareData();
 }
 
 void NodeRareData::IncrementConnectedSubframeCount() {
   SECURITY_CHECK((connected_frame_count_ + 1) <= Page::kMaxNumberOfFrames);
   ++connected_frame_count_;
 }
 
 // Ensure the 10 bits reserved for the m_connectedFrameCount cannot overflow
 static_assert(Page::kMaxNumberOfFrames <
                   (1 << NodeRareData::kConnectedFrameCountBits),
               "Frame limit should fit in rare data count");
 
 }  // namespace blink