[heap] Rework and improve object stats tracing

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 2183 matching lines @@
   MemoryAllocator* memory_allocator_;
 
   StoreBuffer store_buffer_;
 
   IncrementalMarking* incremental_marking_;
 
   GCIdleTimeHandler* gc_idle_time_handler_;
 
   MemoryReducer* memory_reducer_;
 
-  ObjectStats* object_stats_;
+  ObjectStats* live_object_stats_;
+  ObjectStats* dead_object_stats_;
 
   ScavengeJob* scavenge_job_;
 
   AllocationObserver* idle_scavenge_observer_;
 
   // These two counters are monotomically increasing and never reset.
   size_t full_codegen_bytes_generated_;
   size_t crankshaft_codegen_bytes_generated_;
 
   // This counter is increased before each GC and never reset.
@@ skipping 477 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_