Bug 1293572 - Flushing a decoder that is not initialized causes hang. Don't create decoders when the reader is suspened. r=jya

MozReview-Commit-ID: 7ylrYLrrwIS

--HG--
extra : rebase_source : 7421d6b0ee804f30cdfdba0ffda8d9c44d3d7ba5

dom/media/MediaFormatReader.cpp

@@ -388,6 +388,7 @@ bool
 MediaFormatReader::EnsureDecoderCreated(TrackType aTrack)
 {
   MOZ_ASSERT(OnTaskQueue());
+  MOZ_ASSERT(!IsSuspended());
 
   auto& decoder = GetDecoderData(aTrack);
 
@@ -454,6 +455,8 @@ bool
 MediaFormatReader::EnsureDecoderInitialized(TrackType aTrack)
 {
   MOZ_ASSERT(OnTaskQueue());
+  MOZ_ASSERT(!IsSuspended());
+
   auto& decoder = GetDecoderData(aTrack);
 
   if (!decoder.mDecoder || decoder.mInitPromise.Exists()) {
@@ -463,21 +466,14 @@ MediaFormatReader::EnsureDecoderInitialized(TrackType aTrack)
   if (decoder.mDecoderInitialized) {
     return true;
   }
-  if (IsSuspended()) {
-    return false;
-  }
 
   RefPtr<MediaFormatReader> self = this;
   decoder.mInitPromise.Begin(decoder.mDecoder->Init()
        ->Then(OwnerThread(), __func__,
               [self] (TrackType aTrack) {
+                MOZ_ASSERT(!self->IsSuspended());
                 auto& decoder = self->GetDecoderData(aTrack);
                 decoder.mInitPromise.Complete();
-
-                if (self->IsSuspended()) {
-                  return;
-                }
-
                 decoder.mDecoderInitialized = true;
                 MonitorAutoLock mon(decoder.mMonitor);
                 decoder.mDescription = decoder.mDecoder->GetDescriptionName();
@@ -946,6 +942,14 @@ MediaFormatReader::HandleDemuxedSamples(TrackType aTrack,
 {
   MOZ_ASSERT(OnTaskQueue());
 
+  // Don't try to create or initialize decoders
+  // (which might allocate hardware resources) when suspended.
+  if (IsSuspended()) {
+    // Should've deleted decoders when suspended.
+    MOZ_ASSERT(!mAudio.mDecoder && !mVideo.mDecoder);
+    return;
+  }
+
   auto& decoder = GetDecoderData(aTrack);
 
   if (decoder.mQueuedSamples.IsEmpty()) {