Only allow allocation site lifetime transitions from undicided to tenure or don't tenure.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 6c2b5e2c5315f1288108c99f0ff663aa28386b66..1a59dcc1a212077206a35885c0c9353989aafacd 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -1587,7 +1587,10 @@ inline bool AllocationSite::DigestPretenuringFeedback() {
           static_cast<double>(found_count) / create_count : 0.0;
   PretenureFlag current_mode = GetPretenureMode();
 
-  if (minimum_mementos_created) {
+  // TODO(hpayer): Add an intermediate state MAYBE_TENURE which collects
+  // more lifetime feedback for tenuring candidates. In the meantime, we
+  // just allow transitions from undecided to tenured or not tenured.
+  if (minimum_mementos_created && pretenure_decision() == kUndecided) {
     PretenureDecision result = ratio >= kPretenureRatio
         ? kTenure
         : kDontTenure;