--- a/dom/html/HTMLMediaElement.cpp
+++ b/dom/html/HTMLMediaElement.cpp
@@ -199,17 +199,17 @@ protected:
   bool IsCancelled() {
     return mElement->GetCurrentLoadID() != mLoadID;
   }
 
   nsRefPtr<HTMLMediaElement> mElement;
   uint32_t mLoadID;
 };
 
-class nsAsyncEventRunner : public nsMediaEvent
+class HTMLMediaElement::nsAsyncEventRunner : public nsMediaEvent
 {
 private:
   nsString mName;
 
 public:
   nsAsyncEventRunner(const nsAString& aName, HTMLMediaElement* aElement) :
     nsMediaEvent(aElement), mName(aName)
   {

--- a/dom/html/HTMLMediaElement.h
+++ b/dom/html/HTMLMediaElement.h
@@ -212,18 +212,16 @@ public:
   virtual void NotifySuspendedByCache(bool aIsSuspended) MOZ_FINAL MOZ_OVERRIDE;
 
   // Called by the media decoder and the video frame to get the
   // ImageContainer containing the video data.
   virtual VideoFrameContainer* GetVideoFrameContainer() MOZ_FINAL MOZ_OVERRIDE;
   layers::ImageContainer* GetImageContainer();
 
   // Dispatch events
-  using nsGenericHTMLElement::DispatchEvent;
-  virtual nsresult DispatchEvent(const nsAString& aName) MOZ_FINAL MOZ_OVERRIDE;
   virtual nsresult DispatchAsyncEvent(const nsAString& aName) MOZ_FINAL MOZ_OVERRIDE;
 
   // Dispatch events that were raised while in the bfcache
   nsresult DispatchPendingMediaEvents();
 
   // Called by the decoder when some data has been downloaded or
   // buffering/seeking has ended. aNextFrameAvailable is true when
   // the data for the next frame is available. This method will
@@ -975,16 +973,21 @@ protected:
   // in the element's list of text tracks whose text track mode is not disabled
   // and whose text track readiness state is loading.
   void PopulatePendingTextTrackList();
 
   // Gets a reference to the MediaElement's TextTrackManager. If the
   // MediaElement doesn't yet have one then it will create it.
   TextTrackManager* GetOrCreateTextTrackManager();
 
+  class nsAsyncEventRunner;
+  using nsGenericHTMLElement::DispatchEvent;
+  // For nsAsyncEventRunner.
+  nsresult DispatchEvent(const nsAString& aName);
+
   // The current decoder. Load() has been called on this decoder.
   // At most one of mDecoder and mSrcStream can be non-null.
   nsRefPtr<MediaDecoder> mDecoder;
 
   // A reference to the VideoFrameContainer which contains the current frame
   // of video to display.
   nsRefPtr<VideoFrameContainer> mVideoFrameContainer;
 

--- a/dom/media/MediaDecoder.cpp
+++ b/dom/media/MediaDecoder.cpp
@@ -1248,17 +1248,17 @@ void MediaDecoder::DurationChanged()
   mDuration = mDecoderStateMachine ? mDecoderStateMachine->GetDuration() : -1;
   // Duration has changed so we should recompute playback rate
   UpdatePlaybackRate();
 
   SetInfinite(mDuration == -1);
 
   if (mOwner && oldDuration != mDuration && !IsInfinite()) {
     DECODER_LOG("Duration changed to %lld", mDuration);
-    mOwner->DispatchEvent(NS_LITERAL_STRING("durationchange"));
+    mOwner->DispatchAsyncEvent(NS_LITERAL_STRING("durationchange"));
   }
 }
 
 void MediaDecoder::SetDuration(double aDuration)
 {
   MOZ_ASSERT(NS_IsMainThread());
   if (mozilla::IsInfinite(aDuration)) {
     SetInfinite(true);

--- a/dom/media/MediaDecoderOwner.h
+++ b/dom/media/MediaDecoderOwner.h
@@ -16,19 +16,16 @@ class HTMLMediaElement;
 }
 
 class MediaDecoderOwner
 {
 public:
   // Called by the media decoder to indicate that the download is progressing.
   virtual void DownloadProgressed() = 0;
 
-  // Dispatch a synchronous event to the decoder owner
-  virtual nsresult DispatchEvent(const nsAString& aName) = 0;
-
   // Dispatch an asynchronous event to the decoder owner
   virtual nsresult DispatchAsyncEvent(const nsAString& aName) = 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
    * increasing during playback.

--- a/dom/media/gtest/MockMediaDecoderOwner.h
+++ b/dom/media/gtest/MockMediaDecoderOwner.h
@@ -8,20 +8,16 @@
 #include "MediaDecoderOwner.h"
 
 namespace mozilla
 {
 
 class MockMediaDecoderOwner : public MediaDecoderOwner
 {
 public:
-  virtual nsresult DispatchEvent(const nsAString& aName) MOZ_OVERRIDE
-  {
-    return NS_OK;
-  }
   virtual nsresult DispatchAsyncEvent(const nsAString& aName) MOZ_OVERRIDE
   {
     return NS_OK;
   }
   virtual void FireTimeUpdate(bool aPeriodic) MOZ_OVERRIDE {}
   virtual bool GetPaused() MOZ_OVERRIDE { return false; }
   virtual void MetadataLoaded(const MediaInfo* aInfo,
                               nsAutoPtr<const MetadataTags> aTags) MOZ_OVERRIDE