Bug 1165585: Part1. Use AsyncReadmetadata with web audio. r=cpearce

dom/media/webaudio/MediaBufferDecoder.cpp

@@ -126,6 +126,8 @@ private:
   }
 
   void Decode();
+  void OnMetadataRead(MetadataHolder* aMetadata);
+  void OnMetadataNotRead(ReadMetadataFailureReason aReason);
   void RequestSample();
   void SampleDecoded(AudioData* aData);
   void SampleNotDecoded(MediaDecoderReader::NotDecodedReason aReason);
@@ -254,23 +256,32 @@ MediaDecodeTask::Decode()
   // backend support.
   mDecoderReader->SetIgnoreAudioOutputFormat();
 
-  nsAutoPtr<MetadataTags> tags;
-  nsresult rv = mDecoderReader->ReadMetadata(&mMediaInfo, getter_Transfers(tags));
-  if (NS_FAILED(rv)) {
-    mDecoderReader->Shutdown();
-    ReportFailureOnMainThread(WebAudioDecodeJob::InvalidContent);
-    return;
-  }
+  mDecoderReader->AsyncReadMetadata()->Then(mDecoderReader->GetTaskQueue(), __func__, this,
+                                       &MediaDecodeTask::OnMetadataRead,
+                                       &MediaDecodeTask::OnMetadataNotRead);
+}
 
-  if (!mDecoderReader->HasAudio()) {
+void
+MediaDecodeTask::OnMetadataRead(MetadataHolder* aMetadata)
+{
+  mMediaInfo = aMetadata->mInfo;
+  if (!mMediaInfo.HasAudio()) {
     mDecoderReader->Shutdown();
     ReportFailureOnMainThread(WebAudioDecodeJob::NoAudio);
     return;
   }
-
   RequestSample();
 }
 
+void
+MediaDecodeTask::OnMetadataNotRead(ReadMetadataFailureReason aReason)
+{
+  MOZ_RELEASE_ASSERT(aReason != ReadMetadataFailureReason::WAITING_FOR_RESOURCES);
+  mDecoderReader->Shutdown();
+  ReportFailureOnMainThread(WebAudioDecodeJob::InvalidContent);
+  return;
+}
+
 void
 MediaDecodeTask::RequestSample()
 {