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

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 800 matching lines @@
   }
 
   int64_t amount_of_external_allocated_memory() {
     return amount_of_external_allocated_memory_;
   }
 
   void update_amount_of_external_allocated_memory(int64_t delta) {
     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() {
     return new_space_.IsAtMaximumCapacity() && maximum_size_scavenges_ == 0;
   }
 
   void AddWeakObjectToCodeDependency(Handle<HeapObject> obj,
                                      Handle<DependentCode> dep);
 
   DependentCode* LookupWeakObjectToCodeDependency(Handle<HeapObject> obj);
@@ skipping 1147 matching lines @@
 
   void set_force_oom(bool value) { force_oom_ = value; }
 
   // The amount of external memory registered through the API kept alive
   // by global handles
   int64_t amount_of_external_allocated_memory_;
 
   // 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.
   Isolate* isolate_;
 
   Object* roots_[kRootListLength];
 
   size_t code_range_size_;
   int max_semi_space_size_;
   int initial_semispace_size_;
   intptr_t max_old_generation_size_;
@@ skipping 652 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_