Uncommit and shrink semi-spaces only on low allocation rate.

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

Index: src/heap/gc-idle-time-handler.cc
diff --git a/src/heap/gc-idle-time-handler.cc b/src/heap/gc-idle-time-handler.cc
index e88710bd1d10533c8905aab3ef1a8422e95feba2..86587c6fd19671d919a291da07a31a21fcdf4886 100644
--- a/src/heap/gc-idle-time-handler.cc
+++ b/src/heap/gc-idle-time-handler.cc
@@ -58,8 +58,10 @@ void GCIdleTimeHandler::HeapState::Print() {
   PrintF("scavenge_speed=%" V8_PTR_PREFIX "d ", scavenge_speed_in_bytes_per_ms);
   PrintF("new_space_size=%" V8_PTR_PREFIX "d ", used_new_space_size);
   PrintF("new_space_capacity=%" V8_PTR_PREFIX "d ", new_space_capacity);
-  PrintF("new_space_allocation_throughput=%" V8_PTR_PREFIX "d",
+  PrintF("new_space_allocation_throughput=%" V8_PTR_PREFIX "d ",
          new_space_allocation_throughput_in_bytes_per_ms);
+  PrintF("current_new_space_allocation_throughput=%" V8_PTR_PREFIX "d",
+         current_new_space_allocation_throughput_in_bytes_per_ms);
 }