--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -209,16 +209,18 @@ public:
   virtual bool HandleEndOfStream() { return false; }
 
   virtual bool HandleWaitingForData() { return false; }
 
   virtual RefPtr<MediaDecoder::SeekPromise> HandleSeek(SeekTarget aTarget) = 0;
 
   virtual bool HandleAudioCaptured() { return false; }
 
+  virtual RefPtr<ShutdownPromise> HandleShutdown();
+
   virtual void DumpDebugInfo() {}
 
 protected:
   using Master = MediaDecoderStateMachine;
   explicit StateObject(Master* aPtr) : mMaster(aPtr) {}
   TaskQueue* OwnerThread() const { return mMaster->mTaskQueue; }
   MediaResource* Resource() const { return mMaster->mResource; }
   MediaDecoderReaderWrapper* Reader() const { return mMaster->mReader; }
@@ -880,16 +882,22 @@ public:
     return true;
   }
 
   RefPtr<MediaDecoder::SeekPromise> HandleSeek(SeekTarget aTarget) override
   {
     MOZ_DIAGNOSTIC_ASSERT(false, "Can't seek in shutdown state.");
     return MediaDecoder::SeekPromise::CreateAndReject(true, __func__);
   }
+
+  RefPtr<ShutdownPromise> HandleShutdown() override
+  {
+    MOZ_DIAGNOSTIC_ASSERT(false, "Already shutting down.");
+    return nullptr;
+  }
 };
 
 bool
 MediaDecoderStateMachine::
 StateObject::HandleDormant(bool aDormant)
 {
   if (!aDormant) {
     return true;
@@ -901,16 +909,30 @@ StateObject::HandleDormant(bool aDormant
   // SeekJob asserts |mTarget.IsValid() == !mPromise.IsEmpty()| so we
   // need to create the promise even it is not used at all.
   RefPtr<MediaDecoder::SeekPromise> unused =
     mMaster->mQueuedSeek.mPromise.Ensure(__func__);
   SetState<DormantState>();
   return true;
 }
 
+RefPtr<ShutdownPromise>
+MediaDecoderStateMachine::
+StateObject::HandleShutdown()
+{
+  auto master = mMaster;
+  SetState<ShutdownState>();
+
+  return master->mReader->Shutdown()
+    ->Then(master->OwnerThread(), __func__, master,
+           &MediaDecoderStateMachine::FinishShutdown,
+           &MediaDecoderStateMachine::FinishShutdown)
+    ->CompletionPromise();
+}
+
 void
 MediaDecoderStateMachine::
 DecodeMetadataState::OnMetadataRead(MetadataHolder* aMetadata)
 {
   mMetadataRequest.Complete();
 
   // Set mode to PLAYBACK after reading metadata.
   Resource()->SetReadMode(MediaCacheStream::MODE_PLAYBACK);
@@ -2139,26 +2161,17 @@ MediaDecoderStateMachine::SetDormant(boo
   MOZ_ASSERT(OnTaskQueue());
   mStateObj->HandleDormant(aDormant);
 }
 
 RefPtr<ShutdownPromise>
 MediaDecoderStateMachine::Shutdown()
 {
   MOZ_ASSERT(OnTaskQueue());
-
-  mStateObj->SetState<ShutdownState>();
-
-  // Put a task in the decode queue to shutdown the reader.
-  // the queue to spin down.
-  return mReader->Shutdown()
-    ->Then(OwnerThread(), __func__, this,
-           &MediaDecoderStateMachine::FinishShutdown,
-           &MediaDecoderStateMachine::FinishShutdown)
-    ->CompletionPromise();
+  return mStateObj->HandleShutdown();
 }
 
 void MediaDecoderStateMachine::PlayStateChanged()
 {
   MOZ_ASSERT(OnTaskQueue());
 
   if (mPlayState != MediaDecoder::PLAY_STATE_PLAYING) {
     mVideoDecodeSuspendTimer.Reset();