[heap] Improve size profiling for ArrayBuffer tracking

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index e15c1f37e77dfa3dd43b61ed0c2125e93c871c7c..31d228aa6f547b7ebce2b9a51ff79184bfd348db 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -843,14 +843,9 @@ class Heap {
   int64_t external_memory() { return external_memory_; }
   void update_external_memory(int64_t delta) { external_memory_ += delta; }
 
-  void update_external_memory_concurrently_freed(intptr_t freed) {
-    external_memory_concurrently_freed_.Increment(freed);
-  }
+  size_t external_memory_retained_from_new_space();
 
-  void account_external_memory_concurrently_freed() {
-    external_memory_ -= external_memory_concurrently_freed_.Value();
-    external_memory_concurrently_freed_.SetValue(0);
-  }
+  bool ShouldDoScavengeForReducingExternalMemory();
 
   void DeoptMarkedAllocationSites();
 
@@ -1405,6 +1400,8 @@ class Heap {
   void RegisterNewArrayBuffer(JSArrayBuffer* buffer);
   void UnregisterArrayBuffer(JSArrayBuffer* buffer);
 
+  ArrayBufferTracker* array_buffer_tracker() { return array_buffer_tracker_; }
+
   // ===========================================================================
   // Allocation site tracking. =================================================
   // ===========================================================================
@@ -2045,9 +2042,6 @@ class Heap {
   // Caches the amount of external memory registered at the last MC.
   int64_t external_memory_at_last_mark_compact_;
 
-  // The amount of memory that has been freed concurrently.
-  base::AtomicNumber<intptr_t> external_memory_concurrently_freed_;
-
   // This can be calculated directly from a pointer to the heap; however, it is
   // more expedient to get at the isolate directly from within Heap methods.
   Isolate* isolate_;
@@ -2289,6 +2283,9 @@ class Heap {
   // Used for testing purposes.
   bool force_oom_;
 
+  // Tracker for ArrayBuffers pointing to external memory.
+  ArrayBufferTracker* array_buffer_tracker_;
+
   // Classes in "heap" can be friends.
   friend class AlwaysAllocateScope;
   friend class GCCallbacksScope;