Bug 1561486 - shutdown demuxer early. r=alwu

We don't need the demuxer after we've resolved the promise.

Differential Revision: https://phabricator.services.mozilla.com/D36713

--HG--
extra : moz-landing-system : lando

dom/media/Benchmark.cpp

@@ -257,17 +257,12 @@ void BenchmarkPlayback::InitDecoder(UniquePtr<TrackInfo>&& aInfo) {
 void BenchmarkPlayback::FinalizeShutdown() {
   MOZ_ASSERT(OnThread());
 
+  MOZ_ASSERT(mFinished, "GlobalShutdown must have been run");
   MOZ_ASSERT(!mDecoder, "mDecoder must have been shutdown already");
+  MOZ_ASSERT(!mDemuxer, "mDemuxer must have been shutdown already");
   MOZ_DIAGNOSTIC_ASSERT(mDecoderTaskQueue->IsEmpty());
   mDecoderTaskQueue = nullptr;
 
-  if (mTrackDemuxer) {
-    mTrackDemuxer->Reset();
-    mTrackDemuxer->BreakCycles();
-    mTrackDemuxer = nullptr;
-  }
-  mDemuxer = nullptr;
-
   RefPtr<Benchmark> ref(mGlobalState);
   ref->Thread()->Dispatch(NS_NewRunnableFunction(
       "BenchmarkPlayback::FinalizeShutdown", [ref]() { ref->Dispose(); }));
@@ -295,6 +290,13 @@ void BenchmarkPlayback::GlobalShutdown() {
   } else {
     FinalizeShutdown();
   }
+
+  if (mTrackDemuxer) {
+    mTrackDemuxer->Reset();
+    mTrackDemuxer->BreakCycles();
+    mTrackDemuxer = nullptr;
+  }
+  mDemuxer = nullptr;
 }
 
 void BenchmarkPlayback::Output(MediaDataDecoder::DecodedData&& aResults) {