[heap] RecordWrites iterates black object to ensure marking progress.

src/heap/mark-compact-inl.h

Index: src/heap/mark-compact-inl.h
diff --git a/src/heap/mark-compact-inl.h b/src/heap/mark-compact-inl.h
index 5932c6e4fa22873294da5455e91824c918263e23..281ece4cc8d693601e26bd5a6df454064dccfa5a 100644
--- a/src/heap/mark-compact-inl.h
+++ b/src/heap/mark-compact-inl.h
@@ -143,21 +143,10 @@ template <LiveObjectIterationMode T>
 HeapObject* LiveObjectIterator<T>::Next() {
   while (!it_.Done()) {
     HeapObject* object = nullptr;
-    if (T == kGreyObjectsOnBlackPage) {
-      // Black objects will have most of the mark bits set to 1. If we invert
-      // the mark bits, grey objects will be left but the mark bit is moved by
-      // one position. We can just substract one word from the found location
-      // to obtain the grey object.
-      current_cell_ = ~current_cell_;
-    }
     while (current_cell_ != 0) {
       uint32_t trailing_zeros = base::bits::CountTrailingZeros32(current_cell_);
       Address addr = cell_base_ + trailing_zeros * kPointerSize;
 
-      if (T == kGreyObjectsOnBlackPage) {
-        addr -= kPointerSize;
-      }
-
       // Clear the first bit of the found object..
       current_cell_ &= ~(1u << trailing_zeros);
 
@@ -179,14 +168,10 @@ HeapObject* LiveObjectIterator<T>::Next() {
         object = HeapObject::FromAddress(addr);
       } else if (T == kAllLiveObjects) {
         object = HeapObject::FromAddress(addr);
-      } else if (T == kGreyObjectsOnBlackPage) {
-        object = HeapObject::FromAddress(addr);
       }
 
-      if (T != kGreyObjectsOnBlackPage) {
-        // Clear the second bit of the found object.
-        current_cell_ &= ~second_bit_index;
-      }
+      // Clear the second bit of the found object.
+      current_cell_ &= ~second_bit_index;
 
       // We found a live object.
       if (object != nullptr) break;