--- a/dom/media/MediaDecoder.cpp
+++ b/dom/media/MediaDecoder.cpp
@@ -477,17 +477,17 @@ MediaDecoder::SetInfinite(bool aInfinite
 {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(!mShuttingDown);
   mInfiniteStream = aInfinite;
   DurationChanged();
 }
 
 bool
-MediaDecoder::IsInfinite()
+MediaDecoder::IsInfinite() const
 {
   MOZ_ASSERT(NS_IsMainThread());
   return mInfiniteStream;
 }
 
 MediaDecoder::MediaDecoder(MediaDecoderOwner* aOwner)
   : mWatchManager(this, AbstractThread::MainThread())
   , mDormantSupported(false)

--- a/dom/media/MediaDecoder.h
+++ b/dom/media/MediaDecoder.h
@@ -215,34 +215,34 @@ public:
   virtual void AddOutputStream(ProcessedMediaStream* aStream, bool aFinishWhenEnded);
   // Remove an output stream added with AddOutputStream.
   virtual void RemoveOutputStream(MediaStream* aStream);
 
   // Return the duration of the video in seconds.
   virtual double GetDuration();
 
   // Return true if the stream is infinite (see SetInfinite).
-  virtual bool IsInfinite();
+  bool IsInfinite() const;
 
   // Called by MediaResource when some data has been received.
   // Call on the main thread only.
   virtual void NotifyBytesDownloaded();
 
   // Called as data arrives on the stream and is read into the cache.  Called
   // on the main thread only.
   void NotifyDataArrived();
 
   // Return true if we are currently seeking in the media resource.
   // Call on the main thread only.
-  virtual bool IsSeeking() const;
+  bool IsSeeking() const;
 
   // Return true if the decoder has reached the end of playback or the decoder
   // has shutdown.
   // Call on the main thread only.
-  virtual bool IsEndedOrShutdown() const;
+  bool IsEndedOrShutdown() const;
 
   // Return true if the MediaDecoderOwner's error attribute is not null.
   // If the MediaDecoder is shutting down, OwnerHasError will return true.
   bool OwnerHasError() const;
 
   already_AddRefed<GMPCrashHelper> GetCrashHelper() override;
 
 protected: