src: track memory retainer fields

If retainers are embedded in retainers, direct tracking
those lead to double tracking. Instead, use a special tracker
that adjusts the tracking for the container object.

PR-URL: #26161
Reviewed-By: Anna Henningsen <anna@addaleax.net>

src/memory_tracker-inl.h

@@ -241,6 +241,13 @@ void MemoryTracker::Track(const MemoryRetainer* retainer,
   PopNode();
 }
 
+void MemoryTracker::TrackInlineField(const MemoryRetainer* retainer,
+                                     const char* edge_name) {
+  Track(retainer, edge_name);
+  CHECK(CurrentNode());
+  CurrentNode()->size_ -= retainer->SelfSize();
+}
+
 MemoryRetainerNode* MemoryTracker::CurrentNode() const {
   if (node_stack_.empty()) return nullptr;
   return node_stack_.top();

src/memory_tracker.h

@@ -197,6 +197,17 @@ class MemoryTracker {
   inline void Track(const MemoryRetainer* retainer,
                     const char* edge_name = nullptr);
 
+  // Useful for parents that do not wish to perform manual
+  // adjustments to its `SelfSize()` when embedding retainer
+  // objects inline.
+  // Put a memory container into the graph, create an edge from
+  // the current node if there is one on the stack - there should
+  // be one, of the container object which the current field is part of.
+  // Reduce the size of memory from the container so as to avoid
+  // duplication in accounting.
+  inline void TrackInlineField(const MemoryRetainer* retainer,
+                               const char* edge_name = nullptr);
+
   inline v8::EmbedderGraph* graph() { return graph_; }
   inline v8::Isolate* isolate() { return isolate_; }