--- a/dom/media/AccurateSeekTask.h
+++ b/dom/media/AccurateSeekTask.h
@@ -3,17 +3,16 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef ACCURATE_SEEK_TASK_H
 #define ACCURATE_SEEK_TASK_H
 
 #include "SeekTask.h"
-#include "MediaCallbackID.h"
 #include "MediaDecoderReader.h"
 #include "SeekJob.h"
 
 namespace mozilla {
 
 class AccurateSeekTask final : public SeekTask {
 public:
   AccurateSeekTask(const void* aDecoderID,

deleted file mode 100644
--- a/dom/media/MediaCallbackID.cpp
+++ /dev/null
@@ -1,50 +0,0 @@
-#include "MediaCallbackID.h"
-
-namespace mozilla {
-
-char const* CallbackID::INVALID_TAG = "INVALID_TAG";
-int32_t const CallbackID::INVALID_ID = -1;
-
-CallbackID::CallbackID()
-  : mTag(INVALID_TAG), mID(INVALID_ID)
-{
-}
-
-CallbackID::CallbackID(char const* aTag, int32_t aID /* = 0*/)
-  : mTag(aTag), mID(aID)
-{
-}
-
-CallbackID&
-CallbackID::operator++()
-{
-  ++mID;
-  return *this;
-}
-
-CallbackID
-CallbackID::operator++(int)
-{
-  CallbackID ret = *this;
-  ++(*this); // call prefix++
-  return ret;
-}
-
-bool
-CallbackID::operator==(const CallbackID& rhs) const
-{
-  return (strcmp(mTag, rhs.mTag) == 0) && (mID == rhs.mID);
-}
-
-bool
-CallbackID::operator!=(const CallbackID& rhs) const
-{
-  return !(*this == rhs);
-}
-
-CallbackID::operator int() const
-{
-  return mID;
-}
-
-} // namespace mozilla

deleted file mode 100644
--- a/dom/media/MediaCallbackID.h
+++ /dev/null
@@ -1,38 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set ts=8 sts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#ifndef MediaCallbackID_h_
-#define MediaCallbackID_h_
-
-namespace mozilla {
-
-struct CallbackID
-{
-  static char const* INVALID_TAG;
-  static int32_t const INVALID_ID;
-
-  CallbackID();
-
-  explicit CallbackID(char const* aTag, int32_t aID = 0);
-
-  CallbackID& operator++();   // prefix++
-
-  CallbackID operator++(int); // postfix++
-
-  bool operator==(const CallbackID& rhs) const;
-
-  bool operator!=(const CallbackID& rhs) const;
-
-  operator int() const;
-
-private:
-  char const* mTag;
-  int32_t mID;
-};
-
-} // namespace mozilla
-
-#endif // MediaCallbackID_h_

--- a/dom/media/MediaDecoderStateMachine.h
+++ b/dom/media/MediaDecoderStateMachine.h
@@ -83,17 +83,16 @@ hardware (via AudioStream).
 #define MediaDecoderStateMachine_h__
 
 #include "mozilla/Attributes.h"
 #include "mozilla/ReentrantMonitor.h"
 #include "mozilla/StateMirroring.h"
 
 #include "nsAutoPtr.h"
 #include "nsThreadUtils.h"
-#include "MediaCallbackID.h"
 #include "MediaDecoder.h"
 #include "MediaDecoderReader.h"
 #include "MediaDecoderOwner.h"
 #include "MediaEventSource.h"
 #include "MediaMetadataManager.h"
 #include "MediaStatistics.h"
 #include "MediaTimer.h"
 #include "ImageContainer.h"

--- a/dom/media/SeekTask.h
+++ b/dom/media/SeekTask.h
@@ -3,17 +3,16 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef SEEK_TASK_H
 #define SEEK_TASK_H
 
 #include "mozilla/MozPromise.h"
-#include "MediaCallbackID.h"
 #include "SeekTarget.h"
 
 namespace mozilla {
 
 class AbstractThread;
 class MediaData;
 class MediaDecoderReaderWrapper;
 

--- a/dom/media/moz.build
+++ b/dom/media/moz.build
@@ -103,17 +103,16 @@ EXPORTS += [
     'DecoderTraits.h',
     'DOMMediaStream.h',
     'EncodedBufferCache.h',
     'FileBlockCache.h',
     'FrameStatistics.h',
     'Intervals.h',
     'Latency.h',
     'MediaCache.h',
-    'MediaCallbackID.h',
     'MediaData.h',
     'MediaDataDemuxer.h',
     'MediaDecoder.h',
     'MediaDecoderOwner.h',
     'MediaDecoderReader.h',
     'MediaDecoderStateMachine.h',
     'MediaEventSource.h',
     'MediaFormatReader.h',
@@ -217,17 +216,16 @@ UNIFIED_SOURCES += [
     'DecoderDoctorDiagnostics.cpp',
     'DOMMediaStream.cpp',
     'EncodedBufferCache.cpp',
     'FileBlockCache.cpp',
     'GetUserMediaRequest.cpp',
     'GraphDriver.cpp',
     'Latency.cpp',
     'MediaCache.cpp',
-    'MediaCallbackID.cpp',
     'MediaData.cpp',
     'MediaDecoder.cpp',
     'MediaDecoderReader.cpp',
     'MediaDecoderReaderWrapper.cpp',
     'MediaDecoderStateMachine.cpp',
     'MediaDeviceInfo.cpp',
     'MediaDevices.cpp',
     'MediaFormatReader.cpp',