--- a/dom/media/MediaDecoderReaderWrapper.cpp
+++ b/dom/media/MediaDecoderReaderWrapper.cpp
@@ -14,16 +14,17 @@ extern LazyLogModule gMediaDecoderLog;
 #undef LOG
 #define LOG(...) \
   MOZ_LOG(gMediaDecoderLog, mozilla::LogLevel::Debug, (__VA_ARGS__))
 
 // StartTimeRendezvous is a helper class that quarantines the first sample
 // until it gets a sample from both channels, such that we can be guaranteed
 // to know the start time by the time On{Audio,Video}Decoded is called on MDSM.
 class StartTimeRendezvous {
+  typedef MediaDecoderReader::MediaDataPromise MediaDataPromise;
   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(StartTimeRendezvous);
 
 public:
   StartTimeRendezvous(AbstractThread* aOwnerThread,
                       bool aHasAudio,
                       bool aHasVideo,
                       bool aForceZeroStartTime)
     : mOwnerThread(aOwnerThread)
@@ -51,33 +52,27 @@ public:
   RefPtr<HaveStartTimePromise> AwaitStartTime()
   {
     if (HaveStartTime()) {
       return HaveStartTimePromise::CreateAndResolve(true, __func__);
     }
     return mHaveStartTimePromise.Ensure(__func__);
   }
 
-  template<typename PromiseType>
-  struct PromiseSampleType {
-    typedef typename PromiseType::ResolveValueType::element_type Type;
-  };
-
-  template<typename PromiseType, MediaData::Type SampleType>
-  RefPtr<PromiseType>
-  ProcessFirstSample(typename PromiseSampleType<PromiseType>::Type* aData)
+  template<MediaData::Type SampleType>
+  RefPtr<MediaDataPromise>
+  ProcessFirstSample(MediaData* aData)
   {
-    typedef typename PromiseSampleType<PromiseType>::Type DataType;
-    typedef typename PromiseType::Private PromisePrivate;
+    typedef typename MediaDataPromise::Private PromisePrivate;
     MOZ_ASSERT(mOwnerThread->IsCurrentThreadIn());
 
     MaybeSetChannelStartTime<SampleType>(aData->mTime);
 
     RefPtr<PromisePrivate> p = new PromisePrivate(__func__);
-    RefPtr<DataType> data = aData;
+    RefPtr<MediaData> data = aData;
     RefPtr<StartTimeRendezvous> self = this;
     AwaitStartTime()->Then(
       mOwnerThread, __func__,
       [p, data, self] () {
         MOZ_ASSERT(self->mOwnerThread->IsCurrentThreadIn());
         p->Resolve(data, __func__);
       },
       [p] () {
@@ -189,17 +184,17 @@ MediaDecoderReaderWrapper::RequestAudioD
   MOZ_ASSERT(mOwnerThread->IsCurrentThreadIn());
   MOZ_ASSERT(!mShutdown);
 
   auto p = InvokeAsync(mReader->OwnerThread(), mReader.get(), __func__,
                        &MediaDecoderReader::RequestAudioData);
 
   if (!mStartTimeRendezvous->HaveStartTime()) {
     p = p->Then(mOwnerThread, __func__, mStartTimeRendezvous.get(),
-                &StartTimeRendezvous::ProcessFirstSample<MediaDataPromise, MediaData::AUDIO_DATA>,
+                &StartTimeRendezvous::ProcessFirstSample<MediaData::AUDIO_DATA>,
                 &StartTimeRendezvous::FirstSampleRejected<MediaData::AUDIO_DATA>)
          ->CompletionPromise();
   }
 
   return p->Then(mOwnerThread, __func__, this,
                  &MediaDecoderReaderWrapper::OnSampleDecoded,
                  &MediaDecoderReaderWrapper::OnNotDecoded)
           ->CompletionPromise();
@@ -218,17 +213,17 @@ MediaDecoderReaderWrapper::RequestVideoD
   }
 
   auto p = InvokeAsync(mReader->OwnerThread(), mReader.get(), __func__,
                        &MediaDecoderReader::RequestVideoData,
                        aSkipToNextKeyframe, aTimeThreshold.ToMicroseconds());
 
   if (!mStartTimeRendezvous->HaveStartTime()) {
     p = p->Then(mOwnerThread, __func__, mStartTimeRendezvous.get(),
-                &StartTimeRendezvous::ProcessFirstSample<MediaDataPromise, MediaData::VIDEO_DATA>,
+                &StartTimeRendezvous::ProcessFirstSample<MediaData::VIDEO_DATA>,
                 &StartTimeRendezvous::FirstSampleRejected<MediaData::VIDEO_DATA>)
          ->CompletionPromise();
   }
 
   return p->Then(mOwnerThread, __func__, this,
                  &MediaDecoderReaderWrapper::OnSampleDecoded,
                  &MediaDecoderReaderWrapper::OnNotDecoded)
           ->CompletionPromise();

--- a/dom/media/MediaFormatReader.h
+++ b/dom/media/MediaFormatReader.h
@@ -361,43 +361,42 @@ private:
     // Sample format monitoring.
     uint32_t mLastStreamSourceID;
     Maybe<uint32_t> mNextStreamSourceID;
     media::TimeIntervals mTimeRanges;
     Maybe<media::TimeUnit> mLastTimeRangesEnd;
     RefPtr<SharedTrackInfo> mInfo;
   };
 
-  template<typename PromiseType>
   struct DecoderDataWithPromise : public DecoderData {
     DecoderDataWithPromise(MediaFormatReader* aOwner,
                            MediaData::Type aType,
                            uint32_t aDecodeAhead) :
       DecoderData(aOwner, aType, aDecodeAhead)
     {}
 
-    MozPromiseHolder<PromiseType> mPromise;
+    MozPromiseHolder<MediaDataPromise> mPromise;
 
     bool HasPromise() override
     {
       MOZ_ASSERT(mOwner->OnTaskQueue());
       return !mPromise.IsEmpty();
     }
 
     void RejectPromise(MediaDecoderReader::NotDecodedReason aReason,
                        const char* aMethodName) override
     {
       MOZ_ASSERT(mOwner->OnTaskQueue());
       mPromise.Reject(aReason, aMethodName);
       mDecodingRequested = false;
     }
   };
 
-  DecoderDataWithPromise<MediaDataPromise> mAudio;
-  DecoderDataWithPromise<MediaDataPromise> mVideo;
+  DecoderDataWithPromise mAudio;
+  DecoderDataWithPromise mVideo;
 
   // Returns true when the decoder for this track needs input.
   bool NeedInput(DecoderData& aDecoder);
 
   DecoderData& GetDecoderData(TrackType aTrack);
 
   // Demuxer objects.
   RefPtr<MediaDataDemuxer> mDemuxer;