--- a/dom/html/HTMLVideoElement.cpp
+++ b/dom/html/HTMLVideoElement.cpp
@@ -224,30 +224,32 @@ HTMLVideoElement::NotifyOwnerDocumentAct
   UpdateScreenWakeLock();
   return pauseElement;
 }
 
 already_AddRefed<VideoPlaybackQuality>
 HTMLVideoElement::GetVideoPlaybackQuality()
 {
   DOMHighResTimeStamp creationTime = 0;
-  uint64_t totalFrames = 0;
-  uint64_t droppedFrames = 0;
-  uint64_t corruptedFrames = 0;
+  uint32_t totalFrames = 0;
+  uint32_t droppedFrames = 0;
+  uint32_t corruptedFrames = 0;
 
   if (sVideoStatsEnabled) {
     if (nsPIDOMWindowInner* window = OwnerDoc()->GetInnerWindow()) {
       Performance* perf = window->GetPerformance();
       if (perf) {
         creationTime = perf->Now();
       }
     }
 
     if (mDecoder) {
       FrameStatistics& stats = mDecoder->GetFrameStatistics();
+      static_assert(sizeof(uint32_t) >= sizeof (stats.GetParsedFrames()),
+                    "possible truncation from FrameStatistics to VideoPlaybackQuality");
       totalFrames = stats.GetParsedFrames();
       droppedFrames = stats.GetDroppedFrames();
       corruptedFrames = 0;
     }
   }
 
   RefPtr<VideoPlaybackQuality> playbackQuality =
     new VideoPlaybackQuality(this, creationTime, totalFrames, droppedFrames,