--- a/dom/html/HTMLMediaElement.cpp
+++ b/dom/html/HTMLMediaElement.cpp
@@ -6289,26 +6289,27 @@ nsresult HTMLMediaElement::DispatchEvent
 
   return nsContentUtils::DispatchTrustedEvent(OwnerDoc(),
                                               static_cast<nsIContent*>(this),
                                               aName,
                                               false,
                                               false);
 }
 
-nsresult HTMLMediaElement::DispatchAsyncEvent(const nsAString& aName)
+void
+HTMLMediaElement::DispatchAsyncEvent(const nsAString& aName)
 {
   LOG_EVENT(LogLevel::Debug, ("%p Queuing event %s", this,
             NS_ConvertUTF16toUTF8(aName).get()));
 
   // Save events that occur while in the bfcache. These will be dispatched
   // if the page comes out of the bfcache.
   if (mEventDeliveryPaused) {
     mPendingEvents.AppendElement(aName);
-    return NS_OK;
+    return;
   }
 
   nsCOMPtr<nsIRunnable> event;
 
   if (aName.EqualsLiteral("playing")) {
     event = new nsNotifyAboutPlayingRunner(this, TakePendingPlayPromises());
   } else {
     event = new nsAsyncEventRunner(aName, this);
@@ -6323,18 +6324,16 @@ nsresult HTMLMediaElement::DispatchAsync
     }
   } else if (aName.EqualsLiteral("waiting")) {
     mPlayTime.Pause();
     HiddenVideoStop();
   } else if (aName.EqualsLiteral("pause")) {
     mPlayTime.Pause();
     HiddenVideoStop();
   }
-
-  return NS_OK;
 }
 
 nsresult HTMLMediaElement::DispatchPendingMediaEvents()
 {
   NS_ASSERTION(!mEventDeliveryPaused,
                "Must not be in bfcache when dispatching pending media events");
 
   uint32_t count = mPendingEvents.Length();

--- a/dom/html/HTMLMediaElement.h
+++ b/dom/html/HTMLMediaElement.h
@@ -242,17 +242,17 @@ public:
   void UpdateSrcStreamVideoPrincipal(const PrincipalHandle& aPrincipalHandle);
 
   // Called after the MediaStream we're playing rendered a frame to aContainer
   // with a different principalHandle than the previous frame.
   void PrincipalHandleChangedForVideoFrameContainer(VideoFrameContainer* aContainer,
                                                     const PrincipalHandle& aNewPrincipalHandle);
 
   // Dispatch events
-  virtual nsresult DispatchAsyncEvent(const nsAString& aName) final override;
+  virtual void DispatchAsyncEvent(const nsAString& aName) final override;
 
   // Triggers a recomputation of readyState.
   void UpdateReadyState() override { UpdateReadyStateInternal(); }
 
   // Dispatch events that were raised while in the bfcache
   nsresult DispatchPendingMediaEvents();
 
   // Return true if we can activate autoplay assuming enough data has arrived.

--- a/dom/media/MediaDecoderOwner.h
+++ b/dom/media/MediaDecoderOwner.h
@@ -23,17 +23,17 @@ class HTMLMediaElement;
 
 class MediaDecoderOwner
 {
 public:
   // Called by the media decoder to indicate that the download is progressing.
   virtual void DownloadProgressed() = 0;
 
   // Dispatch an asynchronous event to the decoder owner
-  virtual nsresult DispatchAsyncEvent(const nsAString& aName) = 0;
+  virtual void DispatchAsyncEvent(const nsAString& aName) = 0;
 
   // Triggers a recomputation of readyState.
   virtual void UpdateReadyState() = 0;
 
   /**
    * Fires a timeupdate event. If aPeriodic is true, the event will only
    * be fired if we've not fired a timeupdate event (for any reason) in the
    * last 250ms, as required by the spec when the current time is periodically

--- a/dom/media/gtest/MockMediaDecoderOwner.h
+++ b/dom/media/gtest/MockMediaDecoderOwner.h
@@ -9,20 +9,17 @@
 #include "mozilla/AbstractThread.h"
 
 namespace mozilla
 {
 
 class MockMediaDecoderOwner : public MediaDecoderOwner
 {
 public:
-  nsresult DispatchAsyncEvent(const nsAString& aName) override
-  {
-    return NS_OK;
-  }
+  void DispatchAsyncEvent(const nsAString& aName) override {}
   void FireTimeUpdate(bool aPeriodic) override {}
   bool GetPaused() override { return false; }
   void MetadataLoaded(const MediaInfo* aInfo,
                       UniquePtr<const MetadataTags> aTags) override
   {
   }
   void NetworkError() override {}
   void DecodeError(const MediaResult& aError) override {}