[heap] Add a guard for restarting the memory reducer after mark-compact.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 8365d5dc80a3b184b9dbde197c4e5004777667cf..bc501b066e949b933644083f10dc6d49f6a7df85 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -1016,6 +1016,7 @@ bool Heap::CollectGarbage(GarbageCollector collector,
           (committed_memory_before - committed_memory_after) > MB ||
           HasHighFragmentation(used_memory_after, committed_memory_after) ||
           (detached_contexts()->length() > 0);
+      event.committed_memory = committed_memory_after;
       if (deserialization_complete_) {
         memory_reducer_->NotifyMarkCompact(event);
       }