--- a/dom/media/MediaDecoderReader.h
+++ b/dom/media/MediaDecoderReader.h
@@ -159,19 +159,16 @@ public:
   // Tell the reader that the data decoded are not for direct playback, so it
   // can accept more files, in particular those which have more channels than
   // available in the audio output.
   void SetIgnoreAudioOutputFormat()
   {
     mIgnoreAudioOutputFormat = true;
   }
 
-  // MediaSourceReader opts out of the start-time-guessing mechanism.
-  virtual bool ForceZeroStartTime() const { return false; }
-
   // The MediaDecoderStateMachine uses various heuristics that assume that
   // raw media data is arriving sequentially from a network channel. This
   // makes sense in the <video src="foo"> case, but not for more advanced use
   // cases like MSE.
   virtual bool UseBufferingHeuristics() const { return true; }
 
   // Returns the number of bytes of memory allocated by structures/frames in
   // the video queue.

--- a/dom/media/MediaDecoderReaderWrapper.h
+++ b/dom/media/MediaDecoderReaderWrapper.h
@@ -72,17 +72,16 @@ public:
 
   void ReleaseResources();
   void ResetDecode(TrackSet aTracks);
 
   nsresult Init() { return mReader->Init(); }
   bool IsWaitForDataSupported() const { return mReader->IsWaitForDataSupported(); }
   bool IsAsync() const { return mReader->IsAsync(); }
   bool UseBufferingHeuristics() const { return mReader->UseBufferingHeuristics(); }
-  bool ForceZeroStartTime() const { return mReader->ForceZeroStartTime(); }
 
   bool VideoIsHardwareAccelerated() const {
     return mReader->VideoIsHardwareAccelerated();
   }
   TimedMetadataEventSource& TimedMetadataEvent() {
     return mReader->TimedMetadataEvent();
   }
   MediaEventSource<void>& OnMediaNotSeekable() {

--- a/dom/media/MediaFormatReader.cpp
+++ b/dom/media/MediaFormatReader.cpp
@@ -1089,17 +1089,17 @@ MediaFormatReader::OnDemuxerInitDone(nsr
 
   mTags = Move(tags);
   mInitDone = true;
 
   // Try to get the start time.
   // For MSE case, the start time of each track is assumed to be 0.
   // For others, we must demux the first sample to know the start time for each
   // track.
-  if (ForceZeroStartTime()) {
+  if (!mDemuxer->ShouldComputeStartTime()) {
     mAudio.mFirstDemuxedSampleTime.emplace(TimeUnit::FromMicroseconds(0));
     mVideo.mFirstDemuxedSampleTime.emplace(TimeUnit::FromMicroseconds(0));
   } else {
     if (HasAudio()) {
       RequestDemuxSamples(TrackInfo::kAudioTrack);
     }
 
     if (HasVideo()) {
@@ -2629,22 +2629,16 @@ MediaFormatReader::UpdateBuffered()
     // IntervalSet already starts at 0 or is empty, nothing to shift.
     mBuffered = intervals;
   } else {
     mBuffered =
       intervals.Shift(media::TimeUnit() - mInfo.mStartTime);
   }
 }
 
-bool
-MediaFormatReader::ForceZeroStartTime() const
-{
-  return !mDemuxer->ShouldComputeStartTime();
-}
-
 layers::ImageContainer*
 MediaFormatReader::GetImageContainer()
 {
   return mVideoFrameContainer
     ? mVideoFrameContainer->GetImageContainer() : nullptr;
 }
 
 void

--- a/dom/media/MediaFormatReader.h
+++ b/dom/media/MediaFormatReader.h
@@ -48,18 +48,16 @@ public:
 
   RefPtr<SeekPromise> Seek(const SeekTarget& aTarget) override;
 
 protected:
   void NotifyDataArrived() override;
   void UpdateBuffered() override;
 
 public:
-  bool ForceZeroStartTime() const override;
-
   // For Media Resource Management
   void ReleaseResources() override;
 
   nsresult ResetDecode(TrackSet aTracks) override;
 
   RefPtr<ShutdownPromise> Shutdown() override;
 
   bool IsAsync() const override { return true; }