--- a/dom/html/HTMLMediaElement.cpp
+++ b/dom/html/HTMLMediaElement.cpp
@@ -2837,16 +2837,18 @@ HTMLMediaElement::Seek(double aTime,
   // event if it changes the playback position as a result of the seek.
   LOG(LogLevel::Debug, ("%p SetCurrentTime(%f) starting seek", this, aTime));
   nsresult rv = mDecoder->Seek(aTime, aSeekType);
   if (NS_FAILED(rv)) {
     aRv.Throw(rv);
     return nullptr;
   }
 
+  DispatchAsyncEvent(NS_LITERAL_STRING("seeking"));
+
   // We changed whether we're seeking so we need to AddRemoveSelfReference.
   AddRemoveSelfReference();
 
   // Keep the DOM promise.
   mSeekDOMPromise = promise;
 
   return promise.forget();
 }
@@ -5483,21 +5485,16 @@ void HTMLMediaElement::PlaybackEnded()
     // A MediaStream that goes from inactive to active shall be eligible for
     // autoplay again according to the mediacapture-main spec.
     mAutoplaying = true;
   }
 
   DispatchAsyncEvent(NS_LITERAL_STRING("ended"));
 }
 
-void HTMLMediaElement::SeekStarted()
-{
-  DispatchAsyncEvent(NS_LITERAL_STRING("seeking"));
-}
-
 void HTMLMediaElement::SeekCompleted()
 {
   mPlayingBeforeSeek = false;
   SetPlayedOrSeeked(true);
   if (mTextTrackManager) {
     mTextTrackManager->DidSeek();
   }
   FireTimeUpdate(false);

--- a/dom/html/HTMLMediaElement.h
+++ b/dom/html/HTMLMediaElement.h
@@ -191,20 +191,16 @@ public:
   // resource load has been cancelled.
   virtual void LoadAborted() final override;
 
   // Called by the video decoder object, on the main thread,
   // when the video playback has ended.
   virtual void PlaybackEnded() final override;
 
   // Called by the video decoder object, on the main thread,
-  // when the resource has started seeking.
-  virtual void SeekStarted() final override;
-
-  // Called by the video decoder object, on the main thread,
   // when the resource has completed seeking.
   virtual void SeekCompleted() final override;
 
   // Called by the media stream, on the main thread, when the download
   // has been suspended by the cache or because the element itself
   // asked the decoder to suspend the download.
   virtual void DownloadSuspended() final override;
 

--- a/dom/media/MediaDecoder.cpp
+++ b/dom/media/MediaDecoder.cpp
@@ -503,19 +503,16 @@ MediaDecoder::~MediaDecoder()
 
 void
 MediaDecoder::OnPlaybackEvent(MediaEventType aEvent)
 {
   switch (aEvent) {
     case MediaEventType::PlaybackEnded:
       PlaybackEnded();
       break;
-    case MediaEventType::SeekStarted:
-      SeekingStarted();
-      break;
     case MediaEventType::Invalidate:
       Invalidate();
       break;
     case MediaEventType::EnterVideoSuspend:
       GetOwner()->DispatchAsyncEvent(NS_LITERAL_STRING("mozentervideosuspend"));
       break;
     case MediaEventType::ExitVideoSuspend:
       GetOwner()->DispatchAsyncEvent(NS_LITERAL_STRING("mozexitvideosuspend"));
@@ -938,24 +935,16 @@ MediaDecoder::OnSeekRejected()
 {
   MOZ_ASSERT(NS_IsMainThread());
   mSeekRequest.Complete();
   mLogicallySeeking = false;
   GetOwner()->AsyncRejectSeekDOMPromiseIfExists();
 }
 
 void
-MediaDecoder::SeekingStarted()
-{
-  MOZ_ASSERT(NS_IsMainThread());
-  MOZ_DIAGNOSTIC_ASSERT(!IsShutdown());
-  GetOwner()->SeekStarted();
-}
-
-void
 MediaDecoder::ChangeState(PlayState aState)
 {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_ASSERT(!IsShutdown(), "SHUTDOWN is the final state.");
   AbstractThread::AutoEnter context(AbstractMainThread());
 
   if (mNextState == aState) {
     mNextState = PLAY_STATE_PAUSED;

--- a/dom/media/MediaDecoder.h
+++ b/dom/media/MediaDecoder.h
@@ -321,19 +321,16 @@ private:
 
   // Called when the video has completed playing.
   // Call on the main thread only.
   void PlaybackEnded();
 
   void OnSeekRejected();
   void OnSeekResolved();
 
-  // Seeking has started. Inform the element on the main thread.
-  void SeekingStarted();
-
   void UpdateLogicalPositionInternal();
   void UpdateLogicalPosition()
   {
     MOZ_ASSERT(NS_IsMainThread());
     MOZ_DIAGNOSTIC_ASSERT(!IsShutdown());
     // Per spec, offical position remains stable during pause and seek.
     if (mPlayState == PLAY_STATE_PAUSED || IsSeeking()) {
       return;

--- a/dom/media/MediaDecoderOwner.h
+++ b/dom/media/MediaDecoderOwner.h
@@ -79,20 +79,16 @@ public:
   // resource load has been cancelled.
   virtual void LoadAborted() = 0;
 
   // Called by the video decoder object, on the main thread,
   // when the video playback has ended.
   virtual void PlaybackEnded() = 0;
 
   // Called by the video decoder object, on the main thread,
-  // when the resource has started seeking.
-  virtual void SeekStarted() = 0;
-
-  // Called by the video decoder object, on the main thread,
   // when the resource has completed seeking.
   virtual void SeekCompleted() = 0;
 
   // Called by the media stream, on the main thread, when the download
   // has been suspended by the cache or because the element itself
   // asked the decoder to suspend the download.
   virtual void DownloadSuspended() = 0;
 

--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -863,17 +863,16 @@ public:
     // transparent to the user. So we only notify the change when the seek
     // request is from the user.
     if (mVisibility == EventVisibility::Observable) {
       // Don't stop playback for a video-only seek since we want to keep playing
       // audio and we don't need to stop playback while leaving dormant for the
       // playback should has been stopped.
       mMaster->StopPlayback();
       mMaster->UpdatePlaybackPositionInternal(mSeekJob.mTarget->GetTime());
-      mMaster->mOnPlaybackEvent.Notify(MediaEventType::SeekStarted);
       mMaster->UpdateNextFrameStatus(
         MediaDecoderOwner::NEXT_FRAME_UNAVAILABLE_SEEKING);
     }
 
     RefPtr<MediaDecoder::SeekPromise> p = mSeekJob.mPromise.Ensure(__func__);
 
     DoSeek();
 

--- a/dom/media/gtest/MockMediaDecoderOwner.h
+++ b/dom/media/gtest/MockMediaDecoderOwner.h
@@ -24,17 +24,16 @@ public:
                       UniquePtr<const MetadataTags> aTags) override
   {
   }
   void NetworkError() override {}
   void DecodeError(const MediaResult& aError) override {}
   bool HasError() const override { return false; }
   void LoadAborted() override {}
   void PlaybackEnded() override {}
-  void SeekStarted() override {}
   void SeekCompleted() override {}
   void DownloadProgressed() override {}
   void UpdateReadyState() override {}
   void FirstFrameLoaded() override {}
   void DispatchEncrypted(const nsTArray<uint8_t>& aInitData,
                          const nsAString& aInitDataType) override {}
   bool IsActive() const override { return true; }
   bool IsHidden() const override { return false; }