Add Stop() to AudioDecoder.

media/filters/opus_audio_decoder.cc

Index: media/filters/opus_audio_decoder.cc
diff --git a/media/filters/opus_audio_decoder.cc b/media/filters/opus_audio_decoder.cc
index e427c0abacae566b9941bdc6632d0892d573f70f..4337b6474239623c9d440b6b1bae6faad0304b5e 100644
--- a/media/filters/opus_audio_decoder.cc
+++ b/media/filters/opus_audio_decoder.cc
@@ -327,12 +327,21 @@ void OpusAudioDecoder::Reset(const base::Closure& closure) {
   reset_cb.Run();
 }
 
-OpusAudioDecoder::~OpusAudioDecoder() {
-  // TODO(scherkus): should we require Stop() to be called? this might end up
-  // getting called on a random thread due to refcounting.
+void OpusAudioDecoder::Stop(const base::Closure& closure) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  base::Closure stop_cb = BindToCurrentLoop(closure);
+
+  opus_multistream_decoder_ctl(opus_decoder_, OPUS_RESET_STATE);
+  ResetTimestampState();
   CloseDecoder();
+
+  // TODO(rileya): Properly handle the case in which we have a pending
+  // |read_cb_| when Stop() or Reset()-ing.
+  stop_cb.Run();
 }
 
+OpusAudioDecoder::~OpusAudioDecoder() {}
+
 void OpusAudioDecoder::ReadFromDemuxerStream() {
   DCHECK(!read_cb_.is_null());
   demuxer_stream_->Read(base::Bind(&OpusAudioDecoder::BufferReady, weak_this_));