--- a/dom/media/MediaResource.cpp
+++ b/dom/media/MediaResource.cpp
@@ -147,18 +147,18 @@ ChannelMediaResource::Listener::OnStopRe
 
 nsresult
 ChannelMediaResource::Listener::OnDataAvailable(nsIRequest* aRequest,
                                                 nsISupports* aContext,
                                                 nsIInputStream* aStream,
                                                 uint64_t aOffset,
                                                 uint32_t aCount)
 {
-  if (!mResource)
-    return NS_OK;
+  // This might happen off the main thread.
+  MOZ_DIAGNOSTIC_ASSERT(mResource);
   return mResource->OnDataAvailable(aRequest, aStream, aCount);
 }
 
 nsresult
 ChannelMediaResource::Listener::AsyncOnChannelRedirect(nsIChannel* aOldChannel,
                                                        nsIChannel* aNewChannel,
                                                        uint32_t aFlags,
                                                        nsIAsyncVerifyRedirectCallback* cb)
@@ -676,33 +676,33 @@ void ChannelMediaResource::CloseChannel(
 {
   NS_ASSERTION(NS_IsMainThread(), "Only call on main thread");
 
   {
     MutexAutoLock lock(mLock);
     mChannelStatistics.Stop();
   }
 
-  if (mListener) {
-    mListener->Revoke();
-    mListener = nullptr;
-  }
-
   if (mChannel) {
     mSuspendAgent.NotifyChannelClosing();
     // The status we use here won't be passed to the decoder, since
     // we've already revoked the listener. It can however be passed
     // to nsDocumentViewer::LoadComplete if our channel is the one
     // that kicked off creation of a video document. We don't want that
     // document load to think there was an error.
     // NS_ERROR_PARSED_DATA_CACHED is the best thing we have for that
     // at the moment.
     mChannel->Cancel(NS_ERROR_PARSED_DATA_CACHED);
     mChannel = nullptr;
   }
+
+  if (mListener) {
+    mListener->Revoke();
+    mListener = nullptr;
+  }
 }
 
 nsresult ChannelMediaResource::ReadFromCache(char* aBuffer,
                                              int64_t aOffset,
                                              uint32_t aCount)
 {
   return mCacheStream.ReadFromCache(aBuffer, aOffset, aCount);
 }