Dampen old generation allocation limit after scavenge if allocation rate is low.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 270feda587be961ae9fde87ac3f50a7d784d7142..449fb67d456c8179bb7a1f18f436dbfbe72b1c98 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -1177,6 +1177,12 @@ class Heap {
   void SetOldGenerationAllocationLimit(intptr_t old_gen_size, double gc_speed,
                                        double mutator_speed);
 
+  // Decrease the allocation limit if the new limit based on the given
+  // parameters is lower than the current limit.
+  void DampenOldGenerationAllocationLimit(intptr_t old_gen_size,
+                                          double gc_speed,
+                                          double mutator_speed);
+
   // Indicates whether inline bump-pointer allocation has been disabled.
   bool inline_allocation_disabled() { return inline_allocation_disabled_; }