Reland "Make more GCs in idle notification handler."

src/heap.h

Index: src/heap.h
diff --git a/src/heap.h b/src/heap.h
index 70d1ccb7b3652ea968e7397ef97d70ae0d5f9e59..6f04776f7ddaf74f4fbff2d83ddb30c0ec38c3a6 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -2293,7 +2293,6 @@ class Heap {
 
   void StartIdleRound() {
     mark_sweeps_since_idle_round_started_ = 0;
-    ms_count_at_last_idle_notification_ = ms_count_;
   }
 
   void FinishIdleRound() {
@@ -2370,7 +2369,6 @@ class Heap {
   bool last_idle_notification_gc_count_init_;
 
   int mark_sweeps_since_idle_round_started_;
-  int ms_count_at_last_idle_notification_;
   unsigned int gc_count_at_last_idle_gc_;
   int scavenges_since_last_idle_round_;