--- a/dom/media/platforms/PlatformDecoderModule.h
+++ b/dom/media/platforms/PlatformDecoderModule.h
@@ -311,16 +311,28 @@ public:
   {
     return false;
   }
 
   // Return the name of the MediaDataDecoder, only used for decoding.
   // May be accessed in a non thread-safe fashion.
   virtual nsCString GetDescriptionName() const = 0;
 
+  // Return if a decoder needs to be drained in order to output all samples.
+  // Some decoders may buffer samples in order to decode expected future
+  // samples. In these cases the decoder must be drained to ensure all samples
+  // are output when reaching end of stream or running out of data. However,
+  // if a decoder does not buffer samples, then it does not need draining, and
+  // users can avoid doing so, which can benefit performance and simplify code.
+  // Even if a decoder does not require draining, a sane implementation of
+  // Drain() should be specified. It is safe to say a decoder requires draining
+  // even if it does not strictly need it. However bustages will result if a
+  // decoder reports it does not require draining when it does.
+  virtual bool RequiresDrainning() const { return true; }
+
   // Set a hint of seek target time to decoder. Decoder will drop any decoded
   // data which pts is smaller than this value. This threshold needs to be clear
   // after reset decoder.
   // Decoder may not honor this value. However, it'd be better that
   // video decoder implements this API to improve seek performance.
   // Note: it should be called before Input() or after Flush().
   virtual void SetSeekThreshold(const media::TimeUnit& aTime) { }
 

--- a/dom/media/platforms/agnostic/AOMDecoder.h
+++ b/dom/media/platforms/agnostic/AOMDecoder.h
@@ -27,16 +27,20 @@ public:
   RefPtr<DecodePromise> Decode(MediaRawData* aSample) override;
   RefPtr<DecodePromise> Drain() override;
   RefPtr<FlushPromise> Flush() override;
   RefPtr<ShutdownPromise> Shutdown() override;
   nsCString GetDescriptionName() const override
   {
     return NS_LITERAL_CSTRING("av1 libaom video decoder");
   }
+  bool RequiresDrainning() const override
+  {
+    return false;
+  }
 
   // Return true if aMimeType is a one of the strings used
   // by our demuxers to identify AV1 streams.
   static bool IsAV1(const nsACString& aMimeType);
 
   // Return true if aCodecType is a supported codec description.
   static bool IsSupportedCodec(const nsAString& aCodecType);
 

--- a/dom/media/platforms/agnostic/OpusDecoder.h
+++ b/dom/media/platforms/agnostic/OpusDecoder.h
@@ -32,16 +32,20 @@ public:
   RefPtr<DecodePromise> Decode(MediaRawData* aSample) override;
   RefPtr<DecodePromise> Drain() override;
   RefPtr<FlushPromise> Flush() override;
   RefPtr<ShutdownPromise> Shutdown() override;
   nsCString GetDescriptionName() const override
   {
     return NS_LITERAL_CSTRING("opus audio decoder");
   }
+  bool RequiresDrainning() const override
+  {
+    return false;
+  }
 
   // Return true if mimetype is Opus
   static bool IsOpus(const nsACString& aMimeType);
 
   // Pack pre-skip/CodecDelay, given in microseconds, into a
   // MediaByteBuffer. The decoder expects this value to come
   // from the container (if any) and to precede the OpusHead
   // block in the CodecSpecificConfig buffer to verify the

--- a/dom/media/platforms/agnostic/TheoraDecoder.h
+++ b/dom/media/platforms/agnostic/TheoraDecoder.h
@@ -31,16 +31,21 @@ public:
   // Return true if mimetype is a Theora codec
   static bool IsTheora(const nsACString& aMimeType);
 
   nsCString GetDescriptionName() const override
   {
     return NS_LITERAL_CSTRING("theora video decoder");
   }
 
+  bool RequiresDrainning() const override
+  {
+    return false;
+  }
+
 private:
   ~TheoraDecoder();
   nsresult DoDecodeHeader(const unsigned char* aData, size_t aLength);
 
   RefPtr<DecodePromise> ProcessDecode(MediaRawData* aSample);
 
   RefPtr<layers::KnowsCompositor> mImageAllocator;
   RefPtr<layers::ImageContainer> mImageContainer;

--- a/dom/media/platforms/agnostic/VPXDecoder.h
+++ b/dom/media/platforms/agnostic/VPXDecoder.h
@@ -30,16 +30,20 @@ public:
   RefPtr<DecodePromise> Decode(MediaRawData* aSample) override;
   RefPtr<DecodePromise> Drain() override;
   RefPtr<FlushPromise> Flush() override;
   RefPtr<ShutdownPromise> Shutdown() override;
   nsCString GetDescriptionName() const override
   {
     return NS_LITERAL_CSTRING("libvpx video decoder");
   }
+  bool RequiresDrainning() const override
+  {
+    return false;
+  }
 
   enum Codec: uint8_t
   {
     VP8 = 1 << 0,
     VP9 = 1 << 1,
     Unknown = 1 << 7,
   };
 

--- a/dom/media/platforms/agnostic/VorbisDecoder.h
+++ b/dom/media/platforms/agnostic/VorbisDecoder.h
@@ -32,16 +32,20 @@ public:
   RefPtr<DecodePromise> Decode(MediaRawData* aSample) override;
   RefPtr<DecodePromise> Drain() override;
   RefPtr<FlushPromise> Flush() override;
   RefPtr<ShutdownPromise> Shutdown() override;
   nsCString GetDescriptionName() const override
   {
     return NS_LITERAL_CSTRING("vorbis audio decoder");
   }
+  bool RequiresDrainning() const override
+  {
+    return false;
+  }
 
   // Return true if mimetype is Vorbis
   static bool IsVorbis(const nsACString& aMimeType);
   static const AudioConfig::Channel* VorbisLayout(uint32_t aChannels);
 
 private:
   nsresult DecodeHeader(const unsigned char* aData, size_t aLength);
   RefPtr<DecodePromise> ProcessDecode(MediaRawData* aSample);

--- a/dom/media/platforms/agnostic/WAVDecoder.h
+++ b/dom/media/platforms/agnostic/WAVDecoder.h
@@ -27,16 +27,20 @@ public:
   RefPtr<DecodePromise> Decode(MediaRawData* aSample) override;
   RefPtr<DecodePromise> Drain() override;
   RefPtr<FlushPromise> Flush() override;
   RefPtr<ShutdownPromise> Shutdown() override;
   nsCString GetDescriptionName() const override
   {
     return NS_LITERAL_CSTRING("wave audio decoder");
   }
+  bool RequiresDrainning() const override
+  {
+    return false;
+  }
 
 private:
   RefPtr<DecodePromise> ProcessDecode(MediaRawData* aSample);
   const AudioInfo& mInfo;
   const RefPtr<TaskQueue> mTaskQueue;
 };
 
 } // namespace mozilla

--- a/dom/media/platforms/apple/AppleATDecoder.cpp
+++ b/dom/media/platforms/apple/AppleATDecoder.cpp
@@ -110,17 +110,16 @@ AppleATDecoder::Flush()
   LOG("Flushing AudioToolbox AAC decoder");
   return InvokeAsync(mTaskQueue, this, __func__, &AppleATDecoder::ProcessFlush);
 }
 
 RefPtr<MediaDataDecoder::DecodePromise>
 AppleATDecoder::Drain()
 {
   LOG("Draining AudioToolbox AAC decoder");
-  RefPtr<AppleATDecoder> self = this;
   return InvokeAsync(mTaskQueue, __func__, [] {
     return DecodePromise::CreateAndResolve(DecodedData(), __func__);
   });
 }
 
 RefPtr<ShutdownPromise>
 AppleATDecoder::Shutdown()
 {

--- a/dom/media/platforms/apple/AppleATDecoder.h
+++ b/dom/media/platforms/apple/AppleATDecoder.h
@@ -34,16 +34,21 @@ public:
   RefPtr<FlushPromise> Flush() override;
   RefPtr<ShutdownPromise> Shutdown() override;
 
   nsCString GetDescriptionName() const override
   {
     return NS_LITERAL_CSTRING("apple coremedia decoder");
   }
 
+  bool RequiresDrainning() const override
+  {
+    return false;
+  }
+
   // Callbacks also need access to the config.
   const AudioInfo& mConfig;
 
   // Use to extract magic cookie for HE-AAC detection.
   nsTArray<uint8_t> mMagicCookie;
   // Will be set to true should an error occurred while attempting to retrieve
   // the magic cookie property.
   bool mFileStreamError;