Use allocation throughput to estimate next scavenge event in idle notification.

src/heap/gc-idle-time-handler.h

Index: src/heap/gc-idle-time-handler.h
diff --git a/src/heap/gc-idle-time-handler.h b/src/heap/gc-idle-time-handler.h
index bdae3cac957fd0b43cdbef40c0642305150aeb52..473b4742d496d3d1baa5e69d1e12115d620630cb 100644
--- a/src/heap/gc-idle-time-handler.h
+++ b/src/heap/gc-idle-time-handler.h
@@ -132,6 +132,7 @@ class GCIdleTimeHandler {
     size_t scavenge_speed_in_bytes_per_ms;
     size_t available_new_space_memory;
     size_t new_space_capacity;
+    size_t new_space_allocation_throughput_in_bytes_per_ms;
   };
 
   GCIdleTimeHandler()
@@ -161,6 +162,10 @@ class GCIdleTimeHandler {
   static size_t EstimateScavengeTime(size_t new_space_size,
                                      size_t scavenger_speed_in_bytes_per_ms);
 
+  static bool ScavangeMayHappenSoon(
+      size_t available_new_space_memory,
+      size_t new_space_allocation_throughput_in_bytes_per_ms);
+
  private:
   void StartIdleRound() { mark_compacts_since_idle_round_started_ = 0; }
   bool IsMarkCompactIdleRoundFinished() {