--- a/dom/media/MediaDecoderReader.h
+++ b/dom/media/MediaDecoderReader.h
@@ -218,22 +218,16 @@ public:
     return &mBuffered;
   }
 
   TaskQueue* OwnerThread() const
   {
     return mTaskQueue;
   }
 
-  // Returns true if the reader implements RequestAudioData()
-  // and RequestVideoData() asynchronously, rather than using the
-  // implementation in this class to adapt the old synchronous to
-  // the newer async model.
-  virtual bool IsAsync() const = 0;
-
   // Returns true if this decoder reader uses hardware accelerated video
   // decoding.
   virtual bool VideoIsHardwareAccelerated() const = 0;
 
   TimedMetadataEventSource& TimedMetadataEvent()
   {
     return mTimedMetadataEvent;
   }

--- a/dom/media/MediaDecoderReaderWrapper.h
+++ b/dom/media/MediaDecoderReaderWrapper.h
@@ -48,17 +48,16 @@ public:
 
   RefPtr<SeekPromise> Seek(const SeekTarget& aTarget);
   RefPtr<ShutdownPromise> Shutdown();
 
   void ReleaseResources();
   void ResetDecode(TrackSet aTracks);
 
   nsresult Init() { return mReader->Init(); }
-  bool IsAsync() const { return mReader->IsAsync(); }
   bool UseBufferingHeuristics() const { return mReader->UseBufferingHeuristics(); }
 
   bool VideoIsHardwareAccelerated() const {
     return mReader->VideoIsHardwareAccelerated();
   }
   TimedMetadataEventSource& TimedMetadataEvent() {
     return mReader->TimedMetadataEvent();
   }

--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -2250,18 +2250,17 @@ DecodeMetadataState::OnMetadataRead(Meta
   }
 
   // If we don't know the duration by this point, we assume infinity, per spec.
   if (mMaster->mDuration.Ref().isNothing()) {
     mMaster->mDuration = Some(TimeUnit::FromInfinity());
   }
 
   if (mMaster->HasVideo()) {
-    SLOG("Video decode isAsync=%d HWAccel=%d videoQueueSize=%d",
-         Reader()->IsAsync(),
+    SLOG("Video decode HWAccel=%d videoQueueSize=%d",
          Reader()->VideoIsHardwareAccelerated(),
          mMaster->GetAmpleVideoFrames());
   }
 
   MOZ_ASSERT(mMaster->mDuration.Ref().isSome());
 
   mMaster->mMetadataLoadedEvent.Notify(
     Move(aMetadata.mInfo),
@@ -3913,17 +3912,17 @@ MediaDecoderStateMachine::SetAudioCaptur
     ? detail::AMPLE_AUDIO_THRESHOLD / 2 : detail::AMPLE_AUDIO_THRESHOLD;
 
   mStateObj->HandleAudioCaptured();
 }
 
 uint32_t MediaDecoderStateMachine::GetAmpleVideoFrames() const
 {
   MOZ_ASSERT(OnTaskQueue());
-  return (mReader->IsAsync() && mReader->VideoIsHardwareAccelerated())
+  return mReader->VideoIsHardwareAccelerated()
          ? std::max<uint32_t>(sVideoQueueHWAccelSize, MIN_VIDEO_QUEUE_SIZE)
          : std::max<uint32_t>(sVideoQueueDefaultSize, MIN_VIDEO_QUEUE_SIZE);
 }
 
 nsCString
 MediaDecoderStateMachine::GetDebugInfo()
 {
   MOZ_ASSERT(OnTaskQueue());

--- a/dom/media/MediaFormatReader.h
+++ b/dom/media/MediaFormatReader.h
@@ -54,18 +54,16 @@ protected:
 public:
   // For Media Resource Management
   void ReleaseResources() override;
 
   nsresult ResetDecode(TrackSet aTracks) override;
 
   RefPtr<ShutdownPromise> Shutdown() override;
 
-  bool IsAsync() const override { return true; }
-
   bool VideoIsHardwareAccelerated() const override;
 
   bool IsWaitForDataSupported() const override { return true; }
   RefPtr<WaitForDataPromise> WaitForData(MediaData::Type aType) override;
 
   bool UseBufferingHeuristics() const override
   {
     return mTrackDemuxersMayBlock;