--- a/dom/media/MediaResource.h
+++ b/dom/media/MediaResource.h
@@ -457,18 +457,16 @@ public:
   void ThrottleReadahead(bool bThrottle) override;
 
   // Main thread
   nsresult Open(nsIStreamListener** aStreamListener) override;
   nsresult Close() override;
   void     Suspend(bool aCloseImmediately) override;
   void     Resume() override;
   already_AddRefed<nsIPrincipal> GetCurrentPrincipal() override;
-  // Return true if the stream has been closed.
-  bool     IsClosed() const { return mCacheStream.IsClosed(); }
   bool     CanClone() override;
   already_AddRefed<BaseMediaResource> CloneData(
     MediaResourceCallback* aDecoder) override;
   nsresult ReadFromCache(char* aBuffer, int64_t aOffset, uint32_t aCount) override;
 
   // Other thread
   void     SetReadMode(MediaCacheStream::ReadMode aMode) override;
   void     SetPlaybackRate(uint32_t aBytesPerSecond) override;