Introduce an option to do regular new space growing for a while

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index eeb83228610870b1aed5d041ebf2171b65615a5d..f0cbc347ae54340149b845eaaaa56b88e93b2beb 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -1498,6 +1498,7 @@ class Heap {
   int max_semi_space_size_;
   int initial_semispace_size_;
   int target_semispace_size_;
+  int scavenges_before_grow_;
   intptr_t max_old_generation_size_;
   intptr_t max_executable_size_;
   intptr_t maximum_committed_;