New insertion write barrier.

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index e6ec542c9e1f843b66e391f3e85338f187d5c157..2df28c04c07ff4cb662c105a6b7c25b8cb726fcd 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -508,13 +508,6 @@ class MemoryChunk {
     }
   }
 
-  bool IsLeftOfProgressBar(Object** slot) {
-    Address slot_address = reinterpret_cast<Address>(slot);
-    DCHECK(slot_address > this->address());
-    return (slot_address - (this->address() + kObjectStartOffset)) <
-           progress_bar();
-  }
-
   static void IncrementLiveBytesFromGC(Address address, int by) {
     MemoryChunk::FromAddress(address)->IncrementLiveBytes(by);
   }