diff --git a/dom/audiochannel/AudioChannelAgent.cpp b/dom/audiochannel/AudioChannelAgent.cpp
index c02602db25de..3a68bdd371ac 100644
--- a/dom/audiochannel/AudioChannelAgent.cpp
+++ b/dom/audiochannel/AudioChannelAgent.cpp
@@ -35,6 +35,7 @@ NS_IMPL_CYCLE_COLLECTING_RELEASE(AudioChannelAgent)
 
 AudioChannelAgent::AudioChannelAgent()
   : mAudioChannelType(AUDIO_AGENT_CHANNEL_ERROR)
+  , mInnerWindowID(0)
   , mIsRegToService(false)
 {
 }
@@ -104,6 +105,10 @@ AudioChannelAgent::InitInternal(nsIDOMWindow* aWindow, int32_t aChannelType,
   }
 
   if (aWindow) {
+    nsCOMPtr<nsPIDOMWindow> pInnerWindow = do_QueryInterface(aWindow);
+    MOZ_ASSERT(pInnerWindow->IsInnerWindow());
+    mInnerWindowID = pInnerWindow->WindowID();
+
     nsCOMPtr<nsIDOMWindow> topWindow;
     aWindow->GetScriptableTop(getter_AddRefs(topWindow));
     mWindow = do_QueryInterface(topWindow);
@@ -191,3 +196,18 @@ AudioChannelAgent::WindowID() const
 {
   return mWindow ? mWindow->WindowID() : 0;
 }
+
+void
+AudioChannelAgent::WindowAudioCaptureChanged(uint64_t aInnerWindowID)
+{
+  if (aInnerWindowID != mInnerWindowID) {
+    return;
+  }
+
+  nsCOMPtr<nsIAudioChannelAgentCallback> callback = GetCallback();
+  if (!callback) {
+    return;
+  }
+
+  callback->WindowAudioCaptureChanged();
+}
diff --git a/dom/audiochannel/AudioChannelAgent.h b/dom/audiochannel/AudioChannelAgent.h
index 75b2fd335edc..809d34f2a1e7 100644
--- a/dom/audiochannel/AudioChannelAgent.h
+++ b/dom/audiochannel/AudioChannelAgent.h
@@ -34,6 +34,7 @@ public:
   AudioChannelAgent();
 
   void WindowVolumeChanged();
+  void WindowAudioCaptureChanged(uint64_t aInnerWindowID);
 
   nsPIDOMWindow* Window() const
   {
@@ -61,6 +62,7 @@ private:
   nsWeakPtr mWeakCallback;
 
   int32_t mAudioChannelType;
+  uint64_t mInnerWindowID;
   bool mIsRegToService;
 };
 
diff --git a/dom/audiochannel/AudioChannelService.cpp b/dom/audiochannel/AudioChannelService.cpp
index c3b858ab7761..b71b491c5078 100644
--- a/dom/audiochannel/AudioChannelService.cpp
+++ b/dom/audiochannel/AudioChannelService.cpp
@@ -546,6 +546,29 @@ AudioChannelService::RefreshAgentsVolume(nsPIDOMWindow* aWindow)
   }
 }
 
+void
+AudioChannelService::RefreshAgentsCapture(nsPIDOMWindow* aWindow,
+                                          uint64_t aInnerWindowID)
+{
+  MOZ_ASSERT(aWindow);
+  MOZ_ASSERT(aWindow->IsOuterWindow());
+
+  nsCOMPtr<nsIDOMWindow> topWindow;
+  aWindow->GetScriptableTop(getter_AddRefs(topWindow));
+  nsCOMPtr<nsPIDOMWindow> pTopWindow = do_QueryInterface(topWindow);
+  if (!pTopWindow) {
+    return;
+  }
+
+  AudioChannelWindow* winData = GetWindowData(pTopWindow->WindowID());
+
+  nsTObserverArray<AudioChannelAgent*>::ForwardIterator
+    iter(winData->mAgents);
+  while (iter.HasMore()) {
+    iter.GetNext()->WindowAudioCaptureChanged(aInnerWindowID);
+  }
+}
+
 /* static */ const nsAttrValue::EnumTable*
 AudioChannelService::GetAudioChannelTable()
 {
diff --git a/dom/audiochannel/AudioChannelService.h b/dom/audiochannel/AudioChannelService.h
index a0a65d8c737a..4dc0bedb7475 100644
--- a/dom/audiochannel/AudioChannelService.h
+++ b/dom/audiochannel/AudioChannelService.h
@@ -102,6 +102,14 @@ public:
 
   void RefreshAgentsVolume(nsPIDOMWindow* aWindow);
 
+  // This method needs to know the inner window that wants to capture audio. We
+  // group agents per top outer window, but we can have multiple innerWindow per
+  // top outerWindow (subiframes, etc.) and we have to identify all the agents
+  // just for a particular innerWindow.
+  void RefreshAgentsCapture(nsPIDOMWindow* aWindow,
+                            uint64_t aInnerWindowID);
+
+
 #ifdef MOZ_WIDGET_GONK
   void RegisterSpeakerManager(SpeakerManagerService* aSpeakerManager)
   {
diff --git a/dom/audiochannel/nsIAudioChannelAgent.idl b/dom/audiochannel/nsIAudioChannelAgent.idl
index a35f54c09530..87934d4bacc0 100644
--- a/dom/audiochannel/nsIAudioChannelAgent.idl
+++ b/dom/audiochannel/nsIAudioChannelAgent.idl
@@ -6,13 +6,18 @@
 
 interface nsIDOMWindow;
 
-[uuid(4f537c88-3722-4946-9a09-ce559fa0591d)]
+[uuid(5fe83b24-38b9-4901-a4a1-d1bd57d3fe18)]
 interface nsIAudioChannelAgentCallback : nsISupports
 {
   /**
    * Notified when the window volume/mute is changed
    */
   void windowVolumeChanged(in float aVolume, in bool aMuted);
+
+  /**
+   * Notified when the capture state is changed.
+   */
+  void windowAudioCaptureChanged();
 };
 
 /**
diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index 3827f6b57a01..59483a458bd1 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -564,7 +564,7 @@ nsPIDOMWindow::nsPIDOMWindow(nsPIDOMWindow *aOuterWindow)
   mMayHavePointerEnterLeaveEventListener(false),
   mIsModalContentWindow(false),
   mIsActive(false), mIsBackground(false),
-  mAudioMuted(false), mAudioVolume(1.0),
+  mAudioMuted(false), mAudioVolume(1.0), mAudioCaptured(false),
   mDesktopModeViewport(false), mInnerWindow(nullptr),
   mOuterWindow(aOuterWindow),
   // Make sure no actual window ends up with mWindowID == 0
@@ -3745,6 +3745,26 @@ nsPIDOMWindow::RefreshMediaElements()
   service->RefreshAgentsVolume(GetOuterWindow());
 }
 
+bool
+nsPIDOMWindow::GetAudioCaptured() const
+{
+  MOZ_ASSERT(IsInnerWindow());
+  return mAudioCaptured;
+}
+
+nsresult
+nsPIDOMWindow::SetAudioCapture(bool aCapture)
+{
+  MOZ_ASSERT(IsInnerWindow());
+
+  mAudioCaptured = aCapture;
+
+  nsRefPtr<AudioChannelService> service = AudioChannelService::GetOrCreate();
+  service->RefreshAgentsCapture(GetOuterWindow(), mWindowID);
+
+  return NS_OK;
+}
+
 // nsISpeechSynthesisGetter
 
 #ifdef MOZ_WEBSPEECH
diff --git a/dom/base/nsPIDOMWindow.h b/dom/base/nsPIDOMWindow.h
index b9f17bb801a4..3e6404e9950c 100644
--- a/dom/base/nsPIDOMWindow.h
+++ b/dom/base/nsPIDOMWindow.h
@@ -185,6 +185,9 @@ public:
   float GetAudioVolume() const;
   nsresult SetAudioVolume(float aVolume);
 
+  bool GetAudioCaptured() const;
+  nsresult SetAudioCapture(bool aCapture);
+
   virtual void SetServiceWorkersTestingEnabled(bool aEnabled)
   {
     MOZ_ASSERT(IsOuterWindow());
@@ -822,6 +825,8 @@ protected:
   bool                   mAudioMuted;
   float                  mAudioVolume;
 
+  bool                   mAudioCaptured;
+
   // current desktop mode flag.
   bool                   mDesktopModeViewport;
 
diff --git a/dom/fmradio/FMRadio.cpp b/dom/fmradio/FMRadio.cpp
index 1f5d8de3f0e1..150ee703a1f7 100644
--- a/dom/fmradio/FMRadio.cpp
+++ b/dom/fmradio/FMRadio.cpp
@@ -471,6 +471,12 @@ FMRadio::WindowVolumeChanged(float aVolume, bool aMuted)
   return NS_OK;
 }
 
+NS_IMETHODIMP
+FMRadio::WindowAudioCaptureChanged()
+{
+  return NS_OK;
+}
+
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION_INHERITED(FMRadio)
   NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
   NS_INTERFACE_MAP_ENTRY(nsIAudioChannelAgentCallback)
diff --git a/dom/html/HTMLMediaElement.cpp b/dom/html/HTMLMediaElement.cpp
index 493bbd26678a..42c5f63f7774 100644
--- a/dom/html/HTMLMediaElement.cpp
+++ b/dom/html/HTMLMediaElement.cpp
@@ -4492,7 +4492,7 @@ void HTMLMediaElement::UpdateAudioChannelPlayingState()
       if (!mAudioChannelAgent) {
         return;
       }
-      mAudioChannelAgent->InitWithWeakCallback(OwnerDoc()->GetWindow(),
+      mAudioChannelAgent->InitWithWeakCallback(OwnerDoc()->GetInnerWindow(),
                                                static_cast<int32_t>(mAudioChannel),
                                                this);
     }
@@ -4504,6 +4504,10 @@ void HTMLMediaElement::UpdateAudioChannelPlayingState()
 void
 HTMLMediaElement::NotifyAudioChannelAgent(bool aPlaying)
 {
+    // Immediately check if this should go to the MSG instead of the normal
+    // media playback route.
+    WindowAudioCaptureChanged();
+
   // This is needed to pass nsContentUtils::IsCallerChrome().
   // AudioChannel API should not called from content but it can happen that
   // this method has some content JS in its stack.
@@ -4674,6 +4678,15 @@ HTMLMediaElement::GetTopLevelPrincipal()
 }
 #endif // MOZ_EME
 
+NS_IMETHODIMP HTMLMediaElement::WindowAudioCaptureChanged()
+{
+  MOZ_ASSERT(mAudioChannelAgent);
+  DebugOnly<bool> captured = OwnerDoc()->GetInnerWindow()->GetAudioCaptured();
+
+  // Something is going to happen here!!
+  return NS_OK;
+}
+
 AudioTrackList*
 HTMLMediaElement::AudioTracks()
 {
diff --git a/dom/media/webaudio/AudioDestinationNode.cpp b/dom/media/webaudio/AudioDestinationNode.cpp
index 95ab1b413459..3f5a3650a0df 100644
--- a/dom/media/webaudio/AudioDestinationNode.cpp
+++ b/dom/media/webaudio/AudioDestinationNode.cpp
@@ -505,6 +505,21 @@ AudioDestinationNode::WindowVolumeChanged(float aVolume, bool aMuted)
   return NS_OK;
 }
 
+NS_IMETHODIMP
+AudioDestinationNode::WindowAudioCaptureChanged()
+{
+  MOZ_ASSERT(mAudioChannelAgent);
+
+  if (!mStream) {
+    return NS_OK;
+  }
+
+  DebugOnly<bool> captured = GetOwner()->GetAudioCaptured();
+
+  // XXXtodopadenot actually capture
+  return NS_OK;
+}
+
 AudioChannel
 AudioDestinationNode::MozAudioChannelType() const
 {
@@ -591,6 +606,8 @@ AudioDestinationNode::CreateAudioChannelAgent()
   // The AudioChannelAgent must start playing immediately in order to avoid
   // race conditions with mozinterruptbegin/end events.
   InputMuted(false);
+
+  WindowAudioCaptureChanged();
 }
 
 void