diff --git a/dom/audiochannel/AudioChannelService.cpp b/dom/audiochannel/AudioChannelService.cpp
index ae5681ad5bbe..e55136797e18 100644
--- a/dom/audiochannel/AudioChannelService.cpp
+++ b/dom/audiochannel/AudioChannelService.cpp
@@ -43,34 +43,59 @@ namespace {
 // If true, any new AudioChannelAgent will be muted when created.
 bool sAudioChannelMutedByDefault = false;
 
+class NotifyChannelActiveRunnable final : public nsRunnable
+{
+public:
+  NotifyChannelActiveRunnable(uint64_t aWindowID, AudioChannel aAudioChannel,
+                              bool aActive)
+    : mWindowID(aWindowID)
+    , mAudioChannel(aAudioChannel)
+    , mActive(aActive)
+  {}
+
+  NS_IMETHOD Run() override
+  {
+    nsCOMPtr<nsIObserverService> observerService =
+      services::GetObserverService();
+    if (NS_WARN_IF(!observerService)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    nsCOMPtr<nsISupportsPRUint64> wrapper =
+      do_CreateInstance(NS_SUPPORTS_PRUINT64_CONTRACTID);
+    if (NS_WARN_IF(!wrapper)) {
+       return NS_ERROR_FAILURE;
+    }
+
+    wrapper->SetData(mWindowID);
+
+    nsAutoString name;
+    AudioChannelService::GetAudioChannelString(mAudioChannel, name);
+
+    nsAutoCString topic;
+    topic.Assign("audiochannel-activity-");
+    topic.Append(NS_ConvertUTF16toUTF8(name));
+
+    observerService->NotifyObservers(wrapper, topic.get(),
+                                     mActive
+                                       ? MOZ_UTF16("active")
+                                       : MOZ_UTF16("inactive"));
+    return NS_OK;
+  }
+
+private:
+  const uint64_t mWindowID;
+  const AudioChannel mAudioChannel;
+  const bool mActive;
+};
+
 void
 NotifyChannelActive(uint64_t aWindowID, AudioChannel aAudioChannel,
                     bool aActive)
 {
-  nsCOMPtr<nsIObserverService> observerService =
-    services::GetObserverService();
-  if (NS_WARN_IF(!observerService)) {
-    return;
-  }
-
-  nsCOMPtr<nsISupportsPRUint64> wrapper =
-    do_CreateInstance(NS_SUPPORTS_PRUINT64_CONTRACTID);
-  if (!wrapper) {
-     return;
-  }
-
-  wrapper->SetData(aWindowID);
-
-  nsAutoString name;
-  AudioChannelService::GetAudioChannelString(aAudioChannel, name);
-
-  nsAutoCString topic;
-  topic.Assign("audiochannel-activity-");
-  topic.Append(NS_ConvertUTF16toUTF8(name));
-
-  observerService->NotifyObservers(wrapper, topic.get(),
-                                   aActive
-                                     ? MOZ_UTF16("active") : MOZ_UTF16("inactive"));
+  nsRefPtr<nsRunnable> runnable =
+    new NotifyChannelActiveRunnable(aWindowID, aAudioChannel, aActive);
+  NS_DispatchToCurrentThread(runnable);
 }
 
 already_AddRefed<nsPIDOMWindow>
@@ -94,6 +119,34 @@ IsParentProcess()
   return XRE_GetProcessType() == GeckoProcessType_Default;
 }
 
+class MediaPlaybackRunnable : public nsRunnable
+{
+public:
+  MediaPlaybackRunnable(nsIDOMWindow* aWindow, bool aActive)
+    : mWindow(aWindow)
+    , mActive(aActive)
+  {}
+
+ NS_IMETHOD Run()
+ {
+    nsCOMPtr<nsIObserverService> observerService =
+      services::GetObserverService();
+    if (observerService) {
+      observerService->NotifyObservers(
+        ToSupports(mWindow),
+        "media-playback",
+        mActive ? NS_LITERAL_STRING("active").get()
+                : NS_LITERAL_STRING("inactive").get());
+    }
+
+    return NS_OK;
+  }
+
+private:
+  nsCOMPtr<nsIDOMWindow> mWindow;
+  bool mActive;
+};
+
 } // anonymous namespace
 
 StaticRefPtr<AudioChannelService> gAudioChannelService;
@@ -208,13 +261,9 @@ AudioChannelService::RegisterAudioChannelAgent(AudioChannelAgent* aAgent,
 
   // If this is the first agent for this window, we must notify the observers.
   if (winData->mAgents.Length() == 1) {
-    nsCOMPtr<nsIObserverService> observerService =
-      services::GetObserverService();
-    if (observerService) {
-      observerService->NotifyObservers(ToSupports(aAgent->Window()),
-                                       "media-playback",
-                                       NS_LITERAL_STRING("active").get());
-    }
+    nsRefPtr<MediaPlaybackRunnable> runnable =
+      new MediaPlaybackRunnable(aAgent->Window(), true /* active */);
+    NS_DispatchToCurrentThread(runnable);
   }
 
   MaybeSendStatusUpdate();
@@ -258,13 +307,9 @@ AudioChannelService::UnregisterAudioChannelAgent(AudioChannelAgent* aAgent)
 
   // If this is the last agent for this window, we must notify the observers.
   if (winData->mAgents.IsEmpty()) {
-    nsCOMPtr<nsIObserverService> observerService =
-      services::GetObserverService();
-    if (observerService) {
-      observerService->NotifyObservers(ToSupports(aAgent->Window()),
-                                       "media-playback",
-                                       NS_LITERAL_STRING("inactive").get());
-    }
+    nsRefPtr<MediaPlaybackRunnable> runnable =
+      new MediaPlaybackRunnable(aAgent->Window(), false /* active */);
+    NS_DispatchToCurrentThread(runnable);
   }
 
   MaybeSendStatusUpdate();