Introduce a new growth criterion for the new space behind a flag

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index eeb83228610870b1aed5d041ebf2171b65615a5d..20b4955676624ec63b7199176e8ec2a1aeaf4562 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -1195,6 +1195,7 @@ class Heap {
 
   inline void IncrementYoungSurvivorsCounter(int survived) {
     DCHECK(survived >= 0);
+    survived_last_scavenge_ = survived;
     survived_since_last_expansion_ += survived;
   }
 
@@ -1506,6 +1507,9 @@ class Heap {
   // scavenge since last new space expansion.
   int survived_since_last_expansion_;
 
+  // ... and since the last scavenge.
+  int survived_last_scavenge_;
+
   // For keeping track on when to flush RegExp code.
   int sweep_generation_;