An object should only be promoted to the old generation if it survived a scavenge operation.

src/heap-inl.h

Index: src/heap-inl.h
diff --git a/src/heap-inl.h b/src/heap-inl.h
index 64125bc302c7d275133974a54f0566eb0126c916..3198cd7a8fb941ca2a50809d8edc85415ffec563 100644
--- a/src/heap-inl.h
+++ b/src/heap-inl.h
@@ -302,15 +302,12 @@ bool Heap::OldGenerationAllocationLimitReached() {
 
 
 bool Heap::ShouldBePromoted(Address old_address, int object_size) {
-  // An object should be promoted if:
-  // - the object has survived a scavenge operation or
-  // - to space is already 25% full.
+  // An object should be promoted if the object has survived a
+  // scavenge operation.
   NewSpacePage* page = NewSpacePage::FromAddress(old_address);
   Address age_mark = new_space_.age_mark();
-  bool below_mark = page->IsFlagSet(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK) &&
+  return page->IsFlagSet(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK) &&
       (!page->ContainsLimit(age_mark) || old_address < age_mark);
-  return below_mark || (new_space_.Size() + object_size) >=
-                        (new_space_.EffectiveCapacity() >> 2);
 }