--- a/dom/performance/Performance.h
+++ b/dom/performance/Performance.h
@@ -147,21 +147,24 @@ protected:
   void RunNotificationObserversTask();
   void QueueEntry(PerformanceEntry* aEntry);
 
   DOMHighResTimeStamp RoundTime(double aTime) const;
 
   nsTObserverArray<PerformanceObserver*> mObservers;
 
 private:
-  nsTArray<RefPtr<PerformanceEntry>> mUserEntries;
-  nsTArray<RefPtr<PerformanceEntry>> mResourceEntries;
+  static const uint64_t kDefaultResourceTimingBufferSize = 150;
+
+  // When kDefaultResourceTimingBufferSize is increased or removed, these should
+  // be changed to use SegmentedVector
+  AutoTArray<RefPtr<PerformanceEntry>, kDefaultResourceTimingBufferSize> mUserEntries;
+  AutoTArray<RefPtr<PerformanceEntry>, kDefaultResourceTimingBufferSize> mResourceEntries;
 
   uint64_t mResourceTimingBufferSize;
-  static const uint64_t kDefaultResourceTimingBufferSize = 150;
   bool mPendingNotificationObserversTask;
 
   RefPtr<PerformanceService> mPerformanceService;
 };
 
 } // namespace dom
 } // namespace mozilla