Add Stop() to AudioDecoder.

media/filters/ffmpeg_audio_decoder.cc

Index: media/filters/ffmpeg_audio_decoder.cc
diff --git a/media/filters/ffmpeg_audio_decoder.cc b/media/filters/ffmpeg_audio_decoder.cc
index a0e5889eff11aca7e6c84c6bdbf26080ca2fd8c0..47131c2863957d22ec482048fb50b9ef62724db0 100644
--- a/media/filters/ffmpeg_audio_decoder.cc
+++ b/media/filters/ffmpeg_audio_decoder.cc
@@ -115,6 +115,8 @@ void FFmpegAudioDecoder::Read(const ReadCB& read_cb) {
   DCHECK(task_runner_->BelongsToCurrentThread());
   DCHECK(!read_cb.is_null());
   CHECK(read_cb_.is_null()) << "Overlapping decodes are not supported.";
+  DCHECK(stop_cb_.is_null());
+  DCHECK(reset_cb_.is_null());

[xhwang, 2014/01/10 22:14:15]

nit: change the order of these two lines

 
   read_cb_ = BindToCurrentLoop(read_cb);
 
@@ -147,20 +149,28 @@ int FFmpegAudioDecoder::samples_per_second() {
 
 void FFmpegAudioDecoder::Reset(const base::Closure& closure) {
   DCHECK(task_runner_->BelongsToCurrentThread());
-  base::Closure reset_cb = BindToCurrentLoop(closure);
+  reset_cb_ = BindToCurrentLoop(closure);
 
-  avcodec_flush_buffers(codec_context_.get());
-  ResetTimestampState();
-  queued_audio_.clear();
-  reset_cb.Run();
+  if (read_cb_.is_null())
+    DoReset();
+  // Otherwise a demuxer read is pending, we'll wait until it finishes.
 }
 
-FFmpegAudioDecoder::~FFmpegAudioDecoder() {
-  // TODO(scherkus): should we require Stop() to be called? this might end up
-  // getting called on a random thread due to refcounting.
-  ReleaseFFmpegResources();
+void FFmpegAudioDecoder::Stop(const base::Closure& closure) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  stop_cb_ = BindToCurrentLoop(closure);
+
+  if (read_cb_.is_null()) {

[xhwang, 2014/01/10 22:14:15]

We like to check abnormal cases and return early. e.g.

// A demuxer read is pending, we'll wait until it finishes.
if (!read_cb_.is_null())
  return;

.....

+    if (!reset_cb_.is_null())
+      DoReset();

[rileya (GONE FROM CHROMIUM), 2014/01/10 21:35:06]

As-is I don't think(?) this will ever happen (Reset is only deferred if there's
a pending read), but this ensures we have the proper behavior in case that
changes.

[xhwang, 2014/01/10 22:14:15]

That's correct. Feel free to DCHECK here :)

+    else
+      DoStop();
+  }
+  // Otherwise a demuxer read is pending, we'll wait until it finishes.
 }
 
+FFmpegAudioDecoder::~FFmpegAudioDecoder() {}
+
 int FFmpegAudioDecoder::GetAudioBuffer(AVCodecContext* codec,
                                        AVFrame* frame,
                                        int flags) {
@@ -226,6 +236,32 @@ int FFmpegAudioDecoder::GetAudioBuffer(AVCodecContext* codec,
   return 0;
 }
 
+void FFmpegAudioDecoder::DoStop() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK(!stop_cb_.is_null());
+  DCHECK(read_cb_.is_null());
+  DCHECK(reset_cb_.is_null());
+
+  ResetTimestampState();
+  queued_audio_.clear();
+  ReleaseFFmpegResources();
+  base::ResetAndReturn(&stop_cb_).Run();
+}
+
+void FFmpegAudioDecoder::DoReset() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK(!reset_cb_.is_null());
+  DCHECK(read_cb_.is_null());
+
+  avcodec_flush_buffers(codec_context_.get());
+  ResetTimestampState();
+  queued_audio_.clear();
+  base::ResetAndReturn(&reset_cb_).Run();
+
+  if (!stop_cb_.is_null())
+    DoStop();
+}
+
 void FFmpegAudioDecoder::ReadFromDemuxerStream() {
   DCHECK(!read_cb_.is_null());
   demuxer_stream_->Read(base::Bind(
@@ -240,6 +276,24 @@ void FFmpegAudioDecoder::BufferReady(
   DCHECK(queued_audio_.empty());
   DCHECK_EQ(status != DemuxerStream::kOk, !input.get()) << status;
 
+  // Pending Reset: ignore the buffer we just got, send kAborted to |read_cb_|
+  // and carry out the Reset().
+  // If there happens to also be a pending Stop(), that will be handled at
+  // the end of DoReset().
+  if (!reset_cb_.is_null()) {
+    base::ResetAndReturn(&read_cb_).Run(kAborted, NULL);
+    DoReset();
+    return;
+  }
+
+  // Pending Stop: ignore the buffer we just got, send kAborted to |read_cb_|
+  // and carry out the Stop().
+  if (!stop_cb_.is_null()) {
+    base::ResetAndReturn(&read_cb_).Run(kAborted, NULL);
+    DoStop();
+    return;
+  }
+
   if (status == DemuxerStream::kAborted) {
     DCHECK(!input.get());
     base::ResetAndReturn(&read_cb_).Run(kAborted, NULL);