Make sure that idle scavenges are just performed when enough objects are allocated in new space.

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 3beee164f449ff25d8623f204f05696dd10b34bd..e76178b7e676b547dcddf4d4b0e5b0d83f23cde4 100644
--- a/src/heap/gc-idle-time-handler.h
+++ b/src/heap/gc-idle-time-handler.h
@@ -136,6 +136,9 @@ class GCIdleTimeHandler {
   // lower bound for the scavenger speed.
   static const size_t kInitialConservativeScavengeSpeed = 100 * KB;
 
+  // The minimum size of allocated new space objects to trigger a scavenge.
+  static const size_t kMinimumNewSpaceSizeToPerformScavenge = MB / 2;
+
   // If contexts are disposed at a higher rate a full gc is triggered.
   static const double kHighContextDisposalRate;