[heap] Cleanup: Use std::atomic<T> instead of base::AtomicNumber<T> in concurrent marker.

Bug: chromium:842083
Change-Id: I4ce2b58aa7fcafe7e886a3c80d3ddf7bfe3e4415
Reviewed-on: https://chromium-review.googlesource.com/1055389
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53120}

src/heap/concurrent-marking.cc

@@ -577,7 +577,7 @@ void ConcurrentMarking::Run(int task_id, TaskState* task_state) {
     weak_objects_->transition_arrays.FlushToGlobal(task_id);
     weak_objects_->weak_references.FlushToGlobal(task_id);
     base::AsAtomicWord::Relaxed_Store<size_t>(&task_state->marked_bytes, 0);
-    total_marked_bytes_.Increment(marked_bytes);
+    total_marked_bytes_ += marked_bytes;
     {
       base::LockGuard<base::Mutex> guard(&pending_lock_);
       is_pending_[task_id] = false;
@@ -687,7 +687,7 @@ void ConcurrentMarking::FlushLiveBytes(
     live_bytes.clear();
     task_state_[i].marked_bytes = 0;
   }
-  total_marked_bytes_.SetValue(0);
+  total_marked_bytes_ = 0;
 }
 
 void ConcurrentMarking::ClearLiveness(MemoryChunk* chunk) {
@@ -704,7 +704,7 @@ size_t ConcurrentMarking::TotalMarkedBytes() {
     result +=
         base::AsAtomicWord::Relaxed_Load<size_t>(&task_state_[i].marked_bytes);
   }
-  result += total_marked_bytes_.Value();
+  result += total_marked_bytes_;
   return result;
 }
 

src/heap/concurrent-marking.h

@@ -101,7 +101,7 @@ class ConcurrentMarking {
   MarkingWorklist* const on_hold_;
   WeakObjects* const weak_objects_;
   TaskState task_state_[kMaxTasks + 1];
-  base::AtomicNumber<size_t> total_marked_bytes_{0};
+  std::atomic<size_t> total_marked_bytes_{0};
   base::Mutex pending_lock_;
   base::ConditionVariable pending_condition_;
   int pending_task_count_ = 0;