// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/base/pipeline.h"

#include <algorithm>

#include "base/bind.h"
#include "base/callback.h"
#include "base/callback_helpers.h"
#include "base/command_line.h"
#include "base/compiler_specific.h"
#include "base/location.h"
#include "base/metrics/histogram.h"
#include "base/single_thread_task_runner.h"
#include "base/stl_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_util.h"
#include "base/synchronization/condition_variable.h"
#include "media/base/media_log.h"
#include "media/base/media_switches.h"
#include "media/base/renderer.h"
#include "media/base/text_renderer.h"
#include "media/base/text_track_config.h"
#include "media/base/video_decoder_config.h"

using base::TimeDelta;

namespace media {

Pipeline::Pipeline(
    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
    MediaLog* media_log)
    : task_runner_(task_runner),
      media_log_(media_log),
      running_(false),
      did_loading_progress_(false),
      volume_(1.0f),
      playback_rate_(0.0),
      status_(PIPELINE_OK),
      state_(kCreated),
      renderer_ended_(false),
      text_renderer_ended_(false),
      demuxer_(NULL),
      pending_cdm_context_(nullptr),
      weak_factory_(this) {
  media_log_->AddEvent(media_log_->CreatePipelineStateChangedEvent(kCreated));
}

Pipeline::~Pipeline() {
  DCHECK(thread_checker_.CalledOnValidThread())
      << "Pipeline must be destroyed on same thread that created it";
  DCHECK(!running_) << "Stop() must complete before destroying object";
  DCHECK(stop_cb_.is_null());
  DCHECK(seek_cb_.is_null());
}

void Pipeline::Start(Demuxer* demuxer,
                     scoped_ptr<Renderer> renderer,
                     const base::Closure& ended_cb,
                     const PipelineStatusCB& error_cb,
                     const PipelineStatusCB& seek_cb,
                     const PipelineMetadataCB& metadata_cb,
                     const BufferingStateCB& buffering_state_cb,
                     const base::Closure& duration_change_cb,
                     const AddTextTrackCB& add_text_track_cb,
                     const base::Closure& waiting_for_decryption_key_cb) {
  DCHECK(!ended_cb.is_null());
  DCHECK(!error_cb.is_null());
  DCHECK(!seek_cb.is_null());
  DCHECK(!metadata_cb.is_null());
  DCHECK(!buffering_state_cb.is_null());

  base::AutoLock auto_lock(lock_);
  CHECK(!running_) << "Media pipeline is already running";
  running_ = true;

  demuxer_ = demuxer;
  renderer_ = renderer.Pass();
  ended_cb_ = ended_cb;
  error_cb_ = error_cb;
  seek_cb_ = seek_cb;
  metadata_cb_ = metadata_cb;
  buffering_state_cb_ = buffering_state_cb;
  duration_change_cb_ = duration_change_cb;
  add_text_track_cb_ = add_text_track_cb;
  waiting_for_decryption_key_cb_ = waiting_for_decryption_key_cb;

  task_runner_->PostTask(
      FROM_HERE, base::Bind(&Pipeline::StartTask, weak_factory_.GetWeakPtr()));
}

void Pipeline::Stop(const base::Closure& stop_cb) {
  DVLOG(2) << __FUNCTION__;
  task_runner_->PostTask(
      FROM_HERE,
      base::Bind(&Pipeline::StopTask, weak_factory_.GetWeakPtr(), stop_cb));
}

void Pipeline::Seek(TimeDelta time, const PipelineStatusCB& seek_cb) {
  base::AutoLock auto_lock(lock_);
  if (!running_) {
    DLOG(ERROR) << "Media pipeline isn't running. Ignoring Seek().";
    return;
  }

  task_runner_->PostTask(
      FROM_HERE,
      base::Bind(
          &Pipeline::SeekTask, weak_factory_.GetWeakPtr(), time, seek_cb));
}

bool Pipeline::IsRunning() const {
  base::AutoLock auto_lock(lock_);
  return running_;
}

double Pipeline::GetPlaybackRate() const {
  base::AutoLock auto_lock(lock_);
  return playback_rate_;
}

void Pipeline::SetPlaybackRate(double playback_rate) {
  if (playback_rate < 0.0)
    return;

  base::AutoLock auto_lock(lock_);
  playback_rate_ = playback_rate;
  if (running_) {
    task_runner_->PostTask(FROM_HERE,
                           base::Bind(&Pipeline::PlaybackRateChangedTask,
                                      weak_factory_.GetWeakPtr(),
                                      playback_rate));
  }
}

float Pipeline::GetVolume() const {
  base::AutoLock auto_lock(lock_);
  return volume_;
}

void Pipeline::SetVolume(float volume) {
  if (volume < 0.0f || volume > 1.0f)
    return;

  base::AutoLock auto_lock(lock_);
  volume_ = volume;
  if (running_) {
    task_runner_->PostTask(
        FROM_HERE,
        base::Bind(
            &Pipeline::VolumeChangedTask, weak_factory_.GetWeakPtr(), volume));
  }
}

TimeDelta Pipeline::GetMediaTime() const {
  base::AutoLock auto_lock(lock_);
  return renderer_ ? std::min(renderer_->GetMediaTime(), duration_)
                   : TimeDelta();
}

Ranges<TimeDelta> Pipeline::GetBufferedTimeRanges() const {
  base::AutoLock auto_lock(lock_);
  return buffered_time_ranges_;
}

TimeDelta Pipeline::GetMediaDuration() const {
  base::AutoLock auto_lock(lock_);
  return duration_;
}

bool Pipeline::DidLoadingProgress() {
  base::AutoLock auto_lock(lock_);
  bool ret = did_loading_progress_;
  did_loading_progress_ = false;
  return ret;
}

PipelineStatistics Pipeline::GetStatistics() const {
  base::AutoLock auto_lock(lock_);
  return statistics_;
}

void Pipeline::SetCdm(CdmContext* cdm_context,
                      const CdmAttachedCB& cdm_attached_cb) {
  task_runner_->PostTask(
      FROM_HERE, base::Bind(&Pipeline::SetCdmTask, weak_factory_.GetWeakPtr(),
                            cdm_context, cdm_attached_cb));
}

void Pipeline::SetErrorForTesting(PipelineStatus status) {
  OnError(status);
}

bool Pipeline::HasWeakPtrsForTesting() const {
  DCHECK(task_runner_->BelongsToCurrentThread());
  return weak_factory_.HasWeakPtrs();
}

void Pipeline::SetState(State next_state) {
  DVLOG(1) << GetStateString(state_) << " -> " << GetStateString(next_state);

  state_ = next_state;
  media_log_->AddEvent(media_log_->CreatePipelineStateChangedEvent(next_state));
}

#define RETURN_STRING(state) case state: return #state;

const char* Pipeline::GetStateString(State state) {
  switch (state) {
    RETURN_STRING(kCreated);
    RETURN_STRING(kInitDemuxer);
    RETURN_STRING(kInitRenderer);
    RETURN_STRING(kSeeking);
    RETURN_STRING(kPlaying);
    RETURN_STRING(kStopping);
    RETURN_STRING(kStopped);
  }
  NOTREACHED();
  return "INVALID";
}

#undef RETURN_STRING

Pipeline::State Pipeline::GetNextState() const {
  DCHECK(task_runner_->BelongsToCurrentThread());
  DCHECK(stop_cb_.is_null())
      << "State transitions don't happen when stopping";
  DCHECK_EQ(status_, PIPELINE_OK)
      << "State transitions don't happen when there's an error: " << status_;

  switch (state_) {
    case kCreated:
      return kInitDemuxer;

    case kInitDemuxer:
      return kInitRenderer;

    case kInitRenderer:
    case kSeeking:
      return kPlaying;

    case kPlaying:
    case kStopping:
    case kStopped:
      break;
  }
  NOTREACHED() << "State has no transition: " << state_;
  return state_;
}

void Pipeline::OnDemuxerError(PipelineStatus error) {
  task_runner_->PostTask(FROM_HERE,
                         base::Bind(&Pipeline::ErrorChangedTask,
                                    weak_factory_.GetWeakPtr(),
                                    error));
}

void Pipeline::AddTextStream(DemuxerStream* text_stream,
                             const TextTrackConfig& config) {
  task_runner_->PostTask(FROM_HERE,
                         base::Bind(&Pipeline::AddTextStreamTask,
                                    weak_factory_.GetWeakPtr(),
                                    text_stream,
                                    config));
}

void Pipeline::RemoveTextStream(DemuxerStream* text_stream) {
  task_runner_->PostTask(FROM_HERE,
                         base::Bind(&Pipeline::RemoveTextStreamTask,
                                    weak_factory_.GetWeakPtr(),
                                    text_stream));
}

void Pipeline::OnError(PipelineStatus error) {
  DCHECK(task_runner_->BelongsToCurrentThread());
  DCHECK(IsRunning());
  DCHECK_NE(PIPELINE_OK, error);
  VLOG(1) << "Media pipeline error: " << error;

  task_runner_->PostTask(FROM_HERE, base::Bind(
      &Pipeline::ErrorChangedTask, weak_factory_.GetWeakPtr(), error));
}

void Pipeline::SetDuration(TimeDelta duration) {
  DCHECK(IsRunning());
  media_log_->AddEvent(
      media_log_->CreateTimeEvent(
          MediaLogEvent::DURATION_SET, "duration", duration));
  UMA_HISTOGRAM_LONG_TIMES("Media.Duration", duration);

  base::AutoLock auto_lock(lock_);
  duration_ = duration;
  if (!duration_change_cb_.is_null())
    duration_change_cb_.Run();
}

void Pipeline::StateTransitionTask(PipelineStatus status) {
  DCHECK(task_runner_->BelongsToCurrentThread());

  // No-op any state transitions if we're stopping.
  if (state_ == kStopping || state_ == kStopped)
    return;

  // Preserve existing abnormal status, otherwise update based on the result of
  // the previous operation.
  status_ = (status_ != PIPELINE_OK ? status_ : status);

  if (status_ != PIPELINE_OK) {
    ErrorChangedTask(status_);
    return;
  }

  // Guard against accidentally clearing |pending_callbacks_| for states that
  // use it as well as states that should not be using it.
  DCHECK_EQ(pending_callbacks_.get() != NULL, state_ == kSeeking);

  pending_callbacks_.reset();

  PipelineStatusCB done_cb =
      base::Bind(&Pipeline::StateTransitionTask, weak_factory_.GetWeakPtr());

  // Switch states, performing any entrance actions for the new state as well.
  SetState(GetNextState());
  switch (state_) {
    case kInitDemuxer:
      return InitializeDemuxer(done_cb);

    case kInitRenderer:
      // When the state_ transfers to kInitRenderer, it means the demuxer has
      // finished parsing the init info. It should call ReportMetadata in case
      // meeting 'decode' error when passing media segment but WebMediaPlayer's
      // ready_state_ is still ReadyStateHaveNothing. In that case, it will
      // treat it as NetworkStateFormatError not NetworkStateDecodeError.
      ReportMetadata();
      start_timestamp_ = demuxer_->GetStartTime();

      return InitializeRenderer(done_cb);

    case kPlaying:
      DCHECK(start_timestamp_ >= base::TimeDelta());
      renderer_->StartPlayingFrom(start_timestamp_);

      if (text_renderer_)
        text_renderer_->StartPlaying();

      base::ResetAndReturn(&seek_cb_).Run(PIPELINE_OK);

      PlaybackRateChangedTask(GetPlaybackRate());
      VolumeChangedTask(GetVolume());
      return;

    case kStopping:
    case kStopped:
    case kCreated:
    case kSeeking:
      NOTREACHED() << "State has no transition: " << state_;
      return;
  }
}

// Note that the usage of base::Unretained() with the renderers is considered
// safe as they are owned by |pending_callbacks_| and share the same lifetime.
//
// That being said, deleting the renderers while keeping |pending_callbacks_|
// running on the media thread would result in crashes.
void Pipeline::DoSeek(TimeDelta seek_timestamp,
                      const PipelineStatusCB& done_cb) {
  DCHECK(task_runner_->BelongsToCurrentThread());
  DCHECK(!pending_callbacks_.get());
  DCHECK_EQ(state_, kSeeking);
  SerialRunner::Queue bound_fns;

  // Pause.
  if (text_renderer_) {
    bound_fns.Push(base::Bind(
        &TextRenderer::Pause, base::Unretained(text_renderer_.get())));
  }

  // Flush.
  DCHECK(renderer_);
  bound_fns.Push(
      base::Bind(&Renderer::Flush, base::Unretained(renderer_.get())));

  if (text_renderer_) {
    bound_fns.Push(base::Bind(
        &TextRenderer::Flush, base::Unretained(text_renderer_.get())));
  }

  // Seek demuxer.
  bound_fns.Push(base::Bind(
      &Demuxer::Seek, base::Unretained(demuxer_), seek_timestamp));

  pending_callbacks_ = SerialRunner::Run(bound_fns, done_cb);
}

void Pipeline::DoStop(const PipelineStatusCB& done_cb) {
  DVLOG(2) << __FUNCTION__;
  DCHECK(task_runner_->BelongsToCurrentThread());
  DCHECK(!pending_callbacks_.get());

  // TODO(scherkus): Enforce that Renderer is only called on a single thread,
  // even for accessing media time http://crbug.com/370634
  scoped_ptr<Renderer> renderer;
  {
    base::AutoLock auto_lock(lock_);
    renderer.swap(renderer_);
  }
  renderer.reset();
  text_renderer_.reset();

  if (demuxer_) {
    demuxer_->Stop();
    demuxer_ = NULL;
  }

  task_runner_->PostTask(FROM_HERE, base::Bind(done_cb, PIPELINE_OK));
}

void Pipeline::OnStopCompleted(PipelineStatus status) {
  DVLOG(2) << __FUNCTION__;
  DCHECK(task_runner_->BelongsToCurrentThread());
  DCHECK_EQ(state_, kStopping);
  DCHECK(!renderer_);
  DCHECK(!text_renderer_);

  {
    base::AutoLock auto_lock(lock_);
    running_ = false;
  }

  SetState(kStopped);
  demuxer_ = NULL;

  // If we stop during initialization/seeking we want to run |seek_cb_|
  // followed by |stop_cb_| so we don't leave outstanding callbacks around.
  if (!seek_cb_.is_null()) {
    base::ResetAndReturn(&seek_cb_).Run(status_);
    error_cb_.Reset();
  }
  if (!stop_cb_.is_null()) {
    error_cb_.Reset();

    // Invalid all weak pointers so it's safe to destroy |this| on the render
    // main thread.
    weak_factory_.InvalidateWeakPtrs();

    base::ResetAndReturn(&stop_cb_).Run();

    // NOTE: pipeline may be deleted at this point in time as a result of
    // executing |stop_cb_|.
    return;
  }
  if (!error_cb_.is_null()) {
    DCHECK_NE(status_, PIPELINE_OK);
    base::ResetAndReturn(&error_cb_).Run(status_);
  }
}

void Pipeline::AddBufferedTimeRange(TimeDelta start, TimeDelta end) {
  DCHECK(IsRunning());
  base::AutoLock auto_lock(lock_);
  buffered_time_ranges_.Add(start, end);
  did_loading_progress_ = true;
}

// Called from any thread.
void Pipeline::OnUpdateStatistics(const PipelineStatistics& stats) {
  base::AutoLock auto_lock(lock_);
  statistics_.audio_bytes_decoded += stats.audio_bytes_decoded;
  statistics_.video_bytes_decoded += stats.video_bytes_decoded;
  statistics_.video_frames_decoded += stats.video_frames_decoded;
  statistics_.video_frames_dropped += stats.video_frames_dropped;
}

void Pipeline::StartTask() {
  DCHECK(task_runner_->BelongsToCurrentThread());

  CHECK_EQ(kCreated, state_)
      << "Media pipeline cannot be started more than once";

  text_renderer_ = CreateTextRenderer();
  if (text_renderer_) {
    text_renderer_->Initialize(
        base::Bind(&Pipeline::OnTextRendererEnded, weak_factory_.GetWeakPtr()));
  }

  // Set CDM early to avoid unnecessary delay in Renderer::Initialize().
  if (pending_cdm_context_) {
    renderer_->SetCdm(pending_cdm_context_, base::Bind(&IgnoreCdmAttached));
    pending_cdm_context_ = nullptr;
  }

  StateTransitionTask(PIPELINE_OK);
}

void Pipeline::StopTask(const base::Closure& stop_cb) {
  DCHECK(task_runner_->BelongsToCurrentThread());
  DCHECK(stop_cb_.is_null());

  if (state_ == kStopped) {
    // Invalid all weak pointers so it's safe to destroy |this| on the render
    // main thread.
    weak_factory_.InvalidateWeakPtrs();

    // NOTE: pipeline may be deleted at this point in time as a result of
    // executing |stop_cb|.
    stop_cb.Run();

    return;
  }

  stop_cb_ = stop_cb;

  // We may already be stopping due to a runtime error.
  if (state_ == kStopping)
    return;

  // Do not report statistics if the pipeline is not fully initialized.
  if (state_ == kSeeking || state_ == kPlaying) {
    PipelineStatistics stats = GetStatistics();
    if (renderer_->HasVideo() && stats.video_frames_decoded > 0) {
      UMA_HISTOGRAM_COUNTS("Media.DroppedFrameCount",
                           stats.video_frames_dropped);
    }
  }

  SetState(kStopping);
  pending_callbacks_.reset();
  DoStop(base::Bind(&Pipeline::OnStopCompleted, weak_factory_.GetWeakPtr()));
}

void Pipeline::ErrorChangedTask(PipelineStatus error) {
  DCHECK(task_runner_->BelongsToCurrentThread());
  DCHECK_NE(PIPELINE_OK, error) << "PIPELINE_OK isn't an error!";

  media_log_->AddEvent(media_log_->CreatePipelineErrorEvent(error));

  if (state_ == kStopping || state_ == kStopped)
    return;

  SetState(kStopping);
  pending_callbacks_.reset();
  status_ = error;

  DoStop(base::Bind(&Pipeline::OnStopCompleted, weak_factory_.GetWeakPtr()));
}

void Pipeline::PlaybackRateChangedTask(double playback_rate) {
  DCHECK(task_runner_->BelongsToCurrentThread());

  // Playback rate changes are only carried out while playing.
  if (state_ != kPlaying)
    return;

  renderer_->SetPlaybackRate(playback_rate);
}

void Pipeline::VolumeChangedTask(float volume) {
  DCHECK(task_runner_->BelongsToCurrentThread());

  // Volume changes are only carried out while playing.
  if (state_ != kPlaying)
    return;

  renderer_->SetVolume(volume);
}

void Pipeline::SeekTask(TimeDelta time, const PipelineStatusCB& seek_cb) {
  DCHECK(task_runner_->BelongsToCurrentThread());
  DCHECK(stop_cb_.is_null());

  // Suppress seeking if we're not fully started.
  if (state_ != kPlaying) {
    DCHECK(state_ == kStopping || state_ == kStopped)
        << "Receive extra seek in unexpected state: " << state_;

    // TODO(scherkus): should we run the callback?  I'm tempted to say the API
    // will only execute the first Seek() request.
    DVLOG(1) << "Media pipeline has not started, ignoring seek to "
             << time.InMicroseconds() << " (current state: " << state_ << ")";
    return;
  }

  DCHECK(seek_cb_.is_null());

  const base::TimeDelta seek_timestamp =
      std::max(time, demuxer_->GetStartTime());

  SetState(kSeeking);
  seek_cb_ = seek_cb;
  renderer_ended_ = false;
  text_renderer_ended_ = false;
  start_timestamp_ = seek_timestamp;

  DoSeek(seek_timestamp, base::Bind(&Pipeline::StateTransitionTask,
                                    weak_factory_.GetWeakPtr()));
}

void Pipeline::SetCdmTask(CdmContext* cdm_context,
                          const CdmAttachedCB& cdm_attached_cb) {
  base::AutoLock auto_lock(lock_);
  if (!renderer_) {
    pending_cdm_context_ = cdm_context;
    cdm_attached_cb.Run(true);
    return;
  }

  renderer_->SetCdm(cdm_context, cdm_attached_cb);
}

void Pipeline::OnRendererEnded() {
  DCHECK(task_runner_->BelongsToCurrentThread());
  media_log_->AddEvent(media_log_->CreateEvent(MediaLogEvent::ENDED));

  if (state_ != kPlaying)
    return;

  DCHECK(!renderer_ended_);
  renderer_ended_ = true;

  RunEndedCallbackIfNeeded();
}

void Pipeline::OnTextRendererEnded() {
  DCHECK(task_runner_->BelongsToCurrentThread());
  media_log_->AddEvent(media_log_->CreateEvent(MediaLogEvent::TEXT_ENDED));

  if (state_ != kPlaying)
    return;

  DCHECK(!text_renderer_ended_);
  text_renderer_ended_ = true;

  RunEndedCallbackIfNeeded();
}

void Pipeline::RunEndedCallbackIfNeeded() {
  DCHECK(task_runner_->BelongsToCurrentThread());

  if (renderer_ && !renderer_ended_)
    return;

  if (text_renderer_ && text_renderer_->HasTracks() && !text_renderer_ended_)
    return;

  DCHECK_EQ(status_, PIPELINE_OK);
  ended_cb_.Run();
}

scoped_ptr<TextRenderer> Pipeline::CreateTextRenderer() {
  DCHECK(task_runner_->BelongsToCurrentThread());

  const base::CommandLine* cmd_line = base::CommandLine::ForCurrentProcess();
  if (!cmd_line->HasSwitch(switches::kEnableInbandTextTracks))
    return scoped_ptr<media::TextRenderer>();

  return scoped_ptr<media::TextRenderer>(new media::TextRenderer(
      task_runner_,
      base::Bind(&Pipeline::OnAddTextTrack, weak_factory_.GetWeakPtr())));
}

void Pipeline::AddTextStreamTask(DemuxerStream* text_stream,
                                 const TextTrackConfig& config) {
  DCHECK(task_runner_->BelongsToCurrentThread());
  // TODO(matthewjheaney): fix up text_ended_ when text stream
  // is added (http://crbug.com/321446).
  if (text_renderer_)
    text_renderer_->AddTextStream(text_stream, config);
}

void Pipeline::RemoveTextStreamTask(DemuxerStream* text_stream) {
  DCHECK(task_runner_->BelongsToCurrentThread());
  if (text_renderer_)
    text_renderer_->RemoveTextStream(text_stream);
}

void Pipeline::OnAddTextTrack(const TextTrackConfig& config,
                              const AddTextTrackDoneCB& done_cb) {
  DCHECK(task_runner_->BelongsToCurrentThread());
  add_text_track_cb_.Run(config, done_cb);
}

void Pipeline::InitializeDemuxer(const PipelineStatusCB& done_cb) {
  DCHECK(task_runner_->BelongsToCurrentThread());
  demuxer_->Initialize(this, done_cb, text_renderer_);
}

void Pipeline::InitializeRenderer(const PipelineStatusCB& done_cb) {
  DCHECK(task_runner_->BelongsToCurrentThread());

  if (!demuxer_->GetStream(DemuxerStream::AUDIO) &&
      !demuxer_->GetStream(DemuxerStream::VIDEO)) {
    {
      base::AutoLock auto_lock(lock_);
      renderer_.reset();
    }
    OnError(PIPELINE_ERROR_COULD_NOT_RENDER);
    return;
  }

  base::WeakPtr<Pipeline> weak_this = weak_factory_.GetWeakPtr();
  renderer_->Initialize(
      demuxer_,
      done_cb,
      base::Bind(&Pipeline::OnUpdateStatistics, weak_this),
      base::Bind(&Pipeline::BufferingStateChanged, weak_this),
      base::Bind(&Pipeline::OnRendererEnded, weak_this),
      base::Bind(&Pipeline::OnError, weak_this),
      waiting_for_decryption_key_cb_);
}

void Pipeline::ReportMetadata() {
  DCHECK(task_runner_->BelongsToCurrentThread());
  PipelineMetadata metadata;
  metadata.timeline_offset = demuxer_->GetTimelineOffset();
  DemuxerStream* stream = demuxer_->GetStream(DemuxerStream::VIDEO);
  if (stream) {
    metadata.has_video = true;
    metadata.natural_size = stream->video_decoder_config().natural_size();
    metadata.video_rotation = stream->video_rotation();
  }
  if (demuxer_->GetStream(DemuxerStream::AUDIO)) {
    metadata.has_audio = true;
  }
  metadata_cb_.Run(metadata);
}

void Pipeline::BufferingStateChanged(BufferingState new_buffering_state) {
  DVLOG(1) << __FUNCTION__ << "(" << new_buffering_state << ") ";
  DCHECK(task_runner_->BelongsToCurrentThread());
  buffering_state_cb_.Run(new_buffering_state);
}

}  // namespace media