--- a/dom/media/mediasource/TrackBuffersManager.cpp
+++ b/dom/media/mediasource/TrackBuffersManager.cpp
@@ -156,30 +156,22 @@ TrackBuffersManager::BufferAppend()
 void
 TrackBuffersManager::ResetParserState()
 {
   MOZ_ASSERT(NS_IsMainThread());
   MOZ_RELEASE_ASSERT(!mAppendRunning, "Append is running, abort must have been called");
   MSE_DEBUG("");
 
   // 1. If the append state equals PARSING_MEDIA_SEGMENT and the input buffer contains some complete coded frames, then run the coded frame processing algorithm until all of these complete coded frames have been processed.
-  if (mAppendState == AppendState::PARSING_MEDIA_SEGMENT) {
-    nsCOMPtr<nsIRunnable> task =
-      NS_NewRunnableMethod(this, &TrackBuffersManager::FinishCodedFrameProcessing);
-    GetTaskQueue()->Dispatch(task.forget());
-  } else {
-    nsCOMPtr<nsIRunnable> task =
-      NS_NewRunnableMethod(this, &TrackBuffersManager::CompleteResetParserState);
-    GetTaskQueue()->Dispatch(task.forget());
-  }
+  // SourceBuffer.abort() has ensured that all complete coded frames have been
+  // processed. As such, we don't need to check for the value of mAppendState.
+  nsCOMPtr<nsIRunnable> task =
+    NS_NewRunnableMethod(this, &TrackBuffersManager::CompleteResetParserState);
+  GetTaskQueue()->Dispatch(task.forget());
 
-  // Our ResetParserState is really asynchronous, the current task has been
-  // interrupted and will complete shortly (or has already completed).
-  // We must however present to the main thread a stable, reset state.
-  // So we run the following operation now in the main thread.
   // 7. Set append state to WAITING_FOR_SEGMENT.
   SetAppendState(AppendState::WAITING_FOR_SEGMENT);
 }
 
 RefPtr<TrackBuffersManager::RangeRemovalPromise>
 TrackBuffersManager::RangeRemoval(TimeUnit aStart, TimeUnit aEnd)
 {
   MOZ_ASSERT(NS_IsMainThread());
@@ -308,34 +300,16 @@ TrackBuffersManager::Detach()
 void
 TrackBuffersManager::Dump(const char* aPath)
 {
 
 }
 #endif
 
 void
-TrackBuffersManager::FinishCodedFrameProcessing()
-{
-  MOZ_ASSERT(OnTaskQueue());
-
-  if (mProcessingRequest.Exists()) {
-    NS_WARNING("Processing request pending");
-    mProcessingRequest.Disconnect();
-  }
-  // The spec requires us to complete parsing synchronously any outstanding
-  // frames in the current media segment. This can't be implemented in a way
-  // that makes sense.
-  // As such we simply completely ignore the result of any pending input buffer.
-  // TODO: Link to W3C bug.
-
-  CompleteResetParserState();
-}
-
-void
 TrackBuffersManager::CompleteResetParserState()
 {
   MOZ_ASSERT(OnTaskQueue());
   MOZ_RELEASE_ASSERT(!mAppendRunning);
   MSE_DEBUG("");
 
   for (auto& track : GetTracksList()) {
     // 2. Unset the last decode timestamp on all track buffers.

--- a/dom/media/mediasource/TrackBuffersManager.h
+++ b/dom/media/mediasource/TrackBuffersManager.h
@@ -116,19 +116,17 @@ private:
   void CreateDemuxerforMIMEType();
   void ResetDemuxingState();
   void NeedMoreData();
   void RejectAppend(nsresult aRejectValue, const char* aName);
   // Will return a promise that will be resolved once all frames of the current
   // media segment have been processed.
   RefPtr<CodedFrameProcessingPromise> CodedFrameProcessing();
   void CompleteCodedFrameProcessing();
-  // Called by ResetParserState. Complete parsing the input buffer for the
-  // current media segment.
-  void FinishCodedFrameProcessing();
+  // Called by ResetParserState.
   void CompleteResetParserState();
   RefPtr<RangeRemovalPromise>
     CodedFrameRemovalWithPromise(media::TimeInterval aInterval);
   bool CodedFrameRemoval(media::TimeInterval aInterval);
   void SetAppendState(AppendState aAppendState);
 
   bool HasVideo() const
   {