[heap] Allow concurrently transferring colors

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index ff27d09c3aac38b2eedf1bda874fa3d3fc1ebcde..5a57a30a30dd3a7d78fd3999d5a4556005725133 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -670,9 +670,9 @@ class MarkingState {
   MarkingState(Bitmap* bitmap, intptr_t* live_bytes)
       : bitmap_(bitmap), live_bytes_(live_bytes) {}
 
-  void IncrementLiveBytes(intptr_t by) const {
-    *live_bytes_ += static_cast<int>(by);
-  }
+  template <MarkBit::AccessMode mode = MarkBit::NON_ATOMIC>
+  inline void IncrementLiveBytes(intptr_t by) const;
+
   void SetLiveBytes(intptr_t value) const {
     *live_bytes_ = static_cast<int>(value);
   }
@@ -690,6 +690,18 @@ class MarkingState {
   intptr_t* live_bytes_;
 };
 
+template <>
+inline void MarkingState::IncrementLiveBytes<MarkBit::NON_ATOMIC>(
+    intptr_t by) const {
+  *live_bytes_ += by;
+}
+
+template <>
+inline void MarkingState::IncrementLiveBytes<MarkBit::ATOMIC>(
+    intptr_t by) const {
+  reinterpret_cast<base::AtomicNumber<intptr_t>*>(live_bytes_)->Increment(by);
+}
+
 // -----------------------------------------------------------------------------
 // A page is a memory chunk of a size 1MB. Large object pages may be larger.
 //