--- a/dom/media/MediaCache.cpp
+++ b/dom/media/MediaCache.cpp
@@ -2431,17 +2431,17 @@ MediaCacheStream::GetNextCachedData(int6
   MOZ_ASSERT(!NS_IsMainThread());
   AutoLock lock(mMediaCache->Monitor());
   return GetNextCachedDataInternal(lock, aOffset);
 }
 
 int64_t
 MediaCacheStream::GetCachedDataEnd(int64_t aOffset)
 {
-  // TODO: Assert non-main thread.
+  MOZ_ASSERT(!NS_IsMainThread());
   AutoLock lock(mMediaCache->Monitor());
   return GetCachedDataEndInternal(lock, aOffset);
 }
 
 bool
 MediaCacheStream::IsDataCachedToEndOfStream(int64_t aOffset)
 {
   MOZ_ASSERT(!NS_IsMainThread());
@@ -2938,17 +2938,17 @@ nsresult MediaCacheStream::GetCachedRang
       "Must have advanced to start of next range, or hit end of stream");
   }
   return NS_OK;
 }
 
 double
 MediaCacheStream::GetDownloadRate(bool* aIsReliable)
 {
-  // TODO: Assert non-main thread.
+  MOZ_ASSERT(!NS_IsMainThread());
   AutoLock lock(mMediaCache->Monitor());
   return mDownloadStatistics.GetRate(aIsReliable);
 }
 
 nsCString
 MediaCacheStream::GetDebugInfo()
 {
   AutoLock lock(mMediaCache->Monitor());