diff --git a/dom/html/HTMLAudioElement.cpp b/dom/html/HTMLAudioElement.cpp
index 69a2a60d40fe..2572f4011849 100644
--- a/dom/html/HTMLAudioElement.cpp
+++ b/dom/html/HTMLAudioElement.cpp
@@ -20,12 +20,31 @@
 #include "mozilla/dom/TimeRanges.h"
 #include "AudioStream.h"
 
-NS_IMPL_NS_NEW_HTML_ELEMENT(Audio)
+nsGenericHTMLElement* NS_NewHTMLAudioElement(
+    already_AddRefed<mozilla::dom::NodeInfo>&& aNodeInfo,
+    mozilla::dom::FromParser aFromParser) {
+  mozilla::dom::HTMLAudioElement* element =
+      new mozilla::dom::HTMLAudioElement(std::move(aNodeInfo));
+  element->Init();
+  return element;
+}
 
 namespace mozilla {
 namespace dom {
 
-NS_IMPL_ELEMENT_CLONE(HTMLAudioElement)
+nsresult HTMLAudioElement::Clone(mozilla::dom::NodeInfo* aNodeInfo,
+                                 nsINode** aResult) const {
+  *aResult = nullptr;
+  RefPtr<mozilla::dom::NodeInfo> ni(aNodeInfo);
+  HTMLAudioElement* it = new HTMLAudioElement(ni.forget());
+  it->Init();
+  nsCOMPtr<nsINode> kungFuDeathGrip = it;
+  nsresult rv = const_cast<HTMLAudioElement*>(this)->CopyInnerTo(it);
+  if (NS_SUCCEEDED(rv)) {
+    kungFuDeathGrip.swap(*aResult);
+  }
+  return rv;
+}
 
 HTMLAudioElement::HTMLAudioElement(already_AddRefed<NodeInfo>&& aNodeInfo)
     : HTMLMediaElement(std::move(aNodeInfo)) {
@@ -54,7 +73,8 @@ already_AddRefed<HTMLAudioElement> HTMLAudioElement::Audio(
   RefPtr<mozilla::dom::NodeInfo> nodeInfo = doc->NodeInfoManager()->GetNodeInfo(
       nsGkAtoms::audio, nullptr, kNameSpaceID_XHTML, ELEMENT_NODE);
 
-  RefPtr<HTMLAudioElement> audio = new HTMLAudioElement(nodeInfo.forget());
+  RefPtr<HTMLAudioElement> audio =
+      static_cast<HTMLAudioElement*>(NS_NewHTMLAudioElement(nodeInfo.forget()));
   audio->SetHTMLAttr(nsGkAtoms::preload, NS_LITERAL_STRING("auto"), aRv);
   if (aRv.Failed()) {
     return nullptr;
diff --git a/dom/html/HTMLMediaElement.cpp b/dom/html/HTMLMediaElement.cpp
index f305cdcb867b..e1b432c773d4 100644
--- a/dom/html/HTMLMediaElement.cpp
+++ b/dom/html/HTMLMediaElement.cpp
@@ -3498,13 +3498,27 @@ HTMLMediaElement::HTMLMediaElement(
       mShutdownObserver(new ShutdownObserver),
       mPlayed(new TimeRanges(ToSupports(OwnerDoc()))),
       mPaused(true, "HTMLMediaElement::mPaused"),
-      mAudioTrackList(new AudioTrackList(OwnerDoc()->GetParentObject(), this)),
-      mVideoTrackList(new VideoTrackList(OwnerDoc()->GetParentObject(), this)),
       mErrorSink(new ErrorSink(this)),
       mAudioChannelWrapper(new AudioChannelAgentCallback(this)),
       mSink(MakePair(nsString(), RefPtr<AudioDeviceInfo>())) {
   MOZ_ASSERT(mMainThreadEventTarget);
   MOZ_ASSERT(mAbstractMainThread);
+  // Please don't add anything to this constructor or the initialization
+  // list that can cause AddRef to be called. This prevents subclasses
+  // from overriding AddRef in a way that works with our refcount
+  // logging mechanisms. Put these things inside of the ::Init method
+  // instead.
+}
+
+void HTMLMediaElement::Init() {
+  MOZ_ASSERT(mRefCnt == 0 && !mRefCnt.IsPurple(),
+             "HTMLMediaElement::Init called when AddRef has been called "
+             "at least once already, probably in the constructor. Please "
+             "see the documentation in the HTMLMediaElement constructor.");
+  MOZ_ASSERT(!mRefCnt.IsPurple());
+
+  mAudioTrackList = new AudioTrackList(OwnerDoc()->GetParentObject(), this);
+  mVideoTrackList = new VideoTrackList(OwnerDoc()->GetParentObject(), this);
 
   DecoderDoctorLogger::LogConstruction(this);
 
@@ -3525,9 +3539,12 @@ HTMLMediaElement::HTMLMediaElement(
   MediaShutdownManager::InitStatics();
 
   mShutdownObserver->Subscribe(this);
+  mInitialized = true;
 }
 
 HTMLMediaElement::~HTMLMediaElement() {
+  MOZ_ASSERT(mInitialized,
+             "HTMLMediaElement must be initialized before it is destroyed.");
   NS_ASSERTION(
       !mHasSelfReference,
       "How can we be destroyed if we're still holding a self reference?");
diff --git a/dom/html/HTMLMediaElement.h b/dom/html/HTMLMediaElement.h
index ac86a02b8c19..2aba76d77b13 100644
--- a/dom/html/HTMLMediaElement.h
+++ b/dom/html/HTMLMediaElement.h
@@ -117,6 +117,7 @@ class HTMLMediaElement : public nsGenericHTMLElement,
 
   explicit HTMLMediaElement(
       already_AddRefed<mozilla::dom::NodeInfo>&& aNodeInfo);
+  void Init();
 
   void ReportCanPlayTelemetry();
 
@@ -1750,6 +1751,9 @@ class HTMLMediaElement : public nsGenericHTMLElement,
   // threshold.
   void ReportPlayedTimeAfterBlockedTelemetry();
 
+  // True if Init() has been called after construction
+  bool mInitialized = false;
+
   // True if user has called load(), seek() or element has started playing
   // before. It's *only* use for checking autoplay policy
   bool mIsBlessed = false;
diff --git a/dom/html/HTMLVideoElement.cpp b/dom/html/HTMLVideoElement.cpp
index 15b4fd89d307..9e60ce506a93 100644
--- a/dom/html/HTMLVideoElement.cpp
+++ b/dom/html/HTMLVideoElement.cpp
@@ -35,14 +35,33 @@
 #include <algorithm>
 #include <limits>
 
-NS_IMPL_NS_NEW_HTML_ELEMENT(Video)
+nsGenericHTMLElement* NS_NewHTMLVideoElement(
+    already_AddRefed<mozilla::dom::NodeInfo>&& aNodeInfo,
+    mozilla::dom::FromParser aFromParser) {
+  mozilla::dom::HTMLVideoElement* element =
+      new mozilla::dom::HTMLVideoElement(std::move(aNodeInfo));
+  element->Init();
+  return element;
+}
 
 namespace mozilla {
 namespace dom {
 
 static bool sVideoStatsEnabled;
 
-NS_IMPL_ELEMENT_CLONE(HTMLVideoElement)
+nsresult HTMLVideoElement::Clone(mozilla::dom::NodeInfo* aNodeInfo,
+                                 nsINode** aResult) const {
+  *aResult = nullptr;
+  RefPtr<mozilla::dom::NodeInfo> ni(aNodeInfo);
+  HTMLVideoElement* it = new HTMLVideoElement(ni.forget());
+  it->Init();
+  nsCOMPtr<nsINode> kungFuDeathGrip = it;
+  nsresult rv = const_cast<HTMLVideoElement*>(this)->CopyInnerTo(it);
+  if (NS_SUCCEEDED(rv)) {
+    kungFuDeathGrip.swap(*aResult);
+  }
+  return rv;
+}
 
 HTMLVideoElement::HTMLVideoElement(already_AddRefed<NodeInfo>&& aNodeInfo)
     : HTMLMediaElement(std::move(aNodeInfo)), mIsOrientationLocked(false) {
@@ -308,7 +327,8 @@ void HTMLVideoElement::ReleaseVideoWakeLockIfExists() {
   }
 }
 
-void HTMLVideoElement::Init() {
+/* static */
+void HTMLVideoElement::InitStatics() {
   Preferences::AddBoolVarCache(&sVideoStatsEnabled,
                                "media.video_stats.enabled");
 }
diff --git a/dom/html/HTMLVideoElement.h b/dom/html/HTMLVideoElement.h
index 4e18fe68f638..e2acce0b3528 100644
--- a/dom/html/HTMLVideoElement.h
+++ b/dom/html/HTMLVideoElement.h
@@ -38,7 +38,7 @@ class HTMLVideoElement final : public HTMLMediaElement {
                               nsAttrValue& aResult) override;
   NS_IMETHOD_(bool) IsAttributeMapped(const nsAtom* aAttribute) const override;
 
-  static void Init();
+  static void InitStatics();
 
   virtual nsMapRuleToAttributesFunc GetAttributeMappingFunction()
       const override;
diff --git a/layout/build/nsLayoutStatics.cpp b/layout/build/nsLayoutStatics.cpp
index e4b343ef7466..13ee34c9735c 100644
--- a/layout/build/nsLayoutStatics.cpp
+++ b/layout/build/nsLayoutStatics.cpp
@@ -255,7 +255,7 @@ nsresult nsLayoutStatics::Initialize() {
   nsCookieService::AppClearDataObserverInit();
   nsApplicationCacheService::AppClearDataObserverInit();
 
-  HTMLVideoElement::Init();
+  HTMLVideoElement::InitStatics();
   nsGenericHTMLFrameElement::InitStatics();
 
 #ifdef MOZ_XUL