--- a/dom/media/ChannelMediaDecoder.cpp
+++ b/dom/media/ChannelMediaDecoder.cpp
@@ -196,16 +196,17 @@ MediaDecoderStateMachine* ChannelMediaDe
 {
   MOZ_ASSERT(NS_IsMainThread());
   MediaFormatReaderInit init;
   init.mVideoFrameContainer = GetVideoFrameContainer();
   init.mKnowsCompositor = GetCompositor();
   init.mCrashHelper = GetOwner()->CreateGMPCrashHelper();
   init.mFrameStats = mFrameStats;
   init.mResource = mResource;
+  init.mMediaDecoderOwnerID = mOwner;
   mReader = DecoderTraits::CreateReader(ContainerType(), init);
   return new MediaDecoderStateMachine(this, mReader);
 }
 
 void
 ChannelMediaDecoder::Shutdown()
 {
   mWatchManager.Shutdown();

--- a/dom/media/MediaFormatReader.cpp
+++ b/dom/media/MediaFormatReader.cpp
@@ -1109,16 +1109,17 @@ MediaFormatReader::MediaFormatReader(Med
   , mVideoFrameContainer(aInit.mVideoFrameContainer)
   , mCrashHelper(aInit.mCrashHelper)
   , mDecoderFactory(new DecoderFactory(this))
   , mShutdownPromisePool(new ShutdownPromisePool())
   , mBuffered(mTaskQueue,
               TimeIntervals(),
               "MediaFormatReader::mBuffered (Canonical)")
   , mFrameStats(aInit.mFrameStats)
+  , mMediaDecoderOwnerID(aInit.mMediaDecoderOwnerID)
 {
   MOZ_ASSERT(aDemuxer);
   MOZ_COUNT_CTOR(MediaFormatReader);
   mOnTrackWaitingForKeyListener = OnTrackWaitingForKey().Connect(
     mTaskQueue, this, &MediaFormatReader::NotifyWaitingForKey);
 }
 
 MediaFormatReader::~MediaFormatReader()

--- a/dom/media/MediaFormatReader.h
+++ b/dom/media/MediaFormatReader.h
@@ -68,23 +68,27 @@ struct SeekRejectValue
 };
 
 struct MetadataHolder
 {
   UniquePtr<MediaInfo> mInfo;
   UniquePtr<MetadataTags> mTags;
 };
 
+typedef void* MediaDecoderOwnerID;
+
 struct MOZ_STACK_CLASS MediaFormatReaderInit
 {
   MediaResource* mResource = nullptr;
   VideoFrameContainer* mVideoFrameContainer = nullptr;
   FrameStatistics* mFrameStats = nullptr;
   already_AddRefed<layers::KnowsCompositor> mKnowsCompositor;
   already_AddRefed<GMPCrashHelper> mCrashHelper;
+  // Used in bug 1393399 for temporary telemetry.
+  MediaDecoderOwnerID mMediaDecoderOwnerID = nullptr;
 };
 
 class MediaFormatReader final
 {
   static const bool IsExclusive = true;
   typedef TrackInfo::TrackType TrackType;
   typedef MozPromise<bool, MediaResult, IsExclusive> NotifyDataArrivedPromise;
 
@@ -757,13 +761,16 @@ private:
 
   MediaEventProducer<nsTArray<uint8_t>, nsString> mOnEncrypted;
 
   MediaEventProducer<void> mOnWaitingForKey;
 
   MediaEventProducer<MediaResult> mOnDecodeWarning;
 
   RefPtr<FrameStatistics> mFrameStats;
+
+  // Used in bug 1393399 for telemetry.
+  const MediaDecoderOwnerID mMediaDecoderOwnerID;
 };
 
 } // namespace mozilla
 
 #endif

--- a/dom/media/hls/HLSDecoder.cpp
+++ b/dom/media/hls/HLSDecoder.cpp
@@ -88,16 +88,17 @@ HLSDecoder::CreateStateMachine()
 {
   MOZ_ASSERT(NS_IsMainThread());
 
   MediaFormatReaderInit init;
   init.mVideoFrameContainer = GetVideoFrameContainer();
   init.mKnowsCompositor = GetCompositor();
   init.mCrashHelper = GetOwner()->CreateGMPCrashHelper();
   init.mFrameStats = mFrameStats;
+  init.mMediaDecoderOwnerID = mOwner;
   mReader =
     new MediaFormatReader(init, new HLSDemuxer(mHLSResourceWrapper->GetPlayerId()));
 
   return new MediaDecoderStateMachine(this, mReader);
 }
 
 bool
 HLSDecoder::IsEnabled()

--- a/dom/media/mediasource/MediaSourceDecoder.cpp
+++ b/dom/media/mediasource/MediaSourceDecoder.cpp
@@ -37,16 +37,17 @@ MediaSourceDecoder::CreateStateMachine()
 {
   MOZ_ASSERT(NS_IsMainThread());
   mDemuxer = new MediaSourceDemuxer(AbstractMainThread());
   MediaFormatReaderInit init;
   init.mVideoFrameContainer = GetVideoFrameContainer();
   init.mKnowsCompositor = GetCompositor();
   init.mCrashHelper = GetOwner()->CreateGMPCrashHelper();
   init.mFrameStats = mFrameStats;
+  init.mMediaDecoderOwnerID = mOwner;
   mReader = new MediaFormatReader(init, mDemuxer);
   return new MediaDecoderStateMachine(this, mReader);
 }
 
 nsresult
 MediaSourceDecoder::Load(nsIPrincipal* aPrincipal)
 {
   MOZ_ASSERT(NS_IsMainThread());