Perform context disposal garbage collections only if contexts disposals happen at a high rate.

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 edd5e42e263e356579d5b7568fc970a863dace16..1e87e9da17bf34f606d354eb1efdc9af4c8f4aa1 100644
--- a/src/heap/gc-idle-time-handler.h
+++ b/src/heap/gc-idle-time-handler.h
@@ -117,8 +117,12 @@ class GCIdleTimeHandler {
   // lower bound for the scavenger speed.
   static const size_t kInitialConservativeScavengeSpeed = 100 * KB;
 
+  // If contexts are disposed at a higher rate a full gc is triggered.
+  static const double kHighContextDisposalRate;
+
   struct HeapState {
     int contexts_disposed;
+    double contexts_disposal_rate;
     size_t size_of_objects;
     bool incremental_marking_stopped;
     bool can_start_incremental_marking;