Reland of "[heap] Fine-grained JSArrayBuffer tracking"

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 82642266af2a04577c2ee3905a8e682db66d2d3c..150647fbc7c0d2ad31dcc8a36ceaa8e01e54b833 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -818,6 +818,16 @@
     amount_of_external_allocated_memory_ += delta;
   }
 
+  void update_amount_of_external_allocated_freed_memory(intptr_t freed) {
+    amount_of_external_allocated_memory_freed_.Increment(freed);
+  }
+
+  void account_amount_of_external_allocated_freed_memory() {
+    amount_of_external_allocated_memory_ -=
+        amount_of_external_allocated_memory_freed_.Value();
+    amount_of_external_allocated_memory_freed_.SetValue(0);
+  }
+
   void DeoptMarkedAllocationSites();
 
   bool DeoptMaybeTenuredAllocationSites() {
@@ -1984,6 +1994,8 @@
 
   // Caches the amount of external memory registered at the last global gc.
   int64_t amount_of_external_allocated_memory_at_last_global_gc_;
+
+  base::AtomicNumber<intptr_t> amount_of_external_allocated_memory_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.