Caching AudioOutputDevice instances in mixer manager

media/base/audio_renderer_mixer.cc

 // 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/audio_renderer_mixer.h"
 
 #include <cmath>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 
 namespace media {
 
 enum { kPauseDelaySeconds = 10 };
 
-AudioRendererMixer::AudioRendererMixer(
-    const AudioParameters& output_params,
-    const scoped_refptr<AudioRendererSink>& sink)
+AudioRendererMixer::AudioRendererMixer(const AudioParameters& output_params,

[miu, 2016/05/19 22:27:15]

nit: The order of args is opposite the order of the initialized data members. If
this is easy to fix (i.e., there aren't a ton of ctor calls to fix all over the
codebase), then please do.

[o1ka, 2016/05/23 16:16:55]

Done (another way around)

+                                       scoped_refptr<AudioRendererSink> sink)
     : audio_sink_(sink),

[miu, 2016/05/19 22:27:15]

std::move(sink)

[o1ka, 2016/05/23 16:16:54]

Done.

       output_params_(output_params),
       master_converter_(output_params, output_params, true),
       pause_delay_(base::TimeDelta::FromSeconds(kPauseDelaySeconds)),
       last_play_time_(base::TimeTicks::Now()),
       // Initialize |playing_| to true since Start() results in an auto-play.
       playing_(true) {
+  DCHECK(audio_sink_);
   audio_sink_->Initialize(output_params, this);
   audio_sink_->Start();
 }
 
 AudioRendererMixer::~AudioRendererMixer() {
-  // AudioRendererSinks must be stopped before being destructed.
+  // AudioRendererSink must be stopped before mixer is destructed.
   audio_sink_->Stop();
 
   // Ensure that all mixer inputs have removed themselves prior to destruction.
   DCHECK(master_converter_.empty());
   DCHECK(converters_.empty());
   DCHECK_EQ(error_callbacks_.size(), 0U);
 }
 
 void AudioRendererMixer::AddMixerInput(const AudioParameters& input_params,
                                        AudioConverter::InputCallback* input) {
@@ skipping 102 matching lines @@
 }
 
 void AudioRendererMixer::OnRenderError() {
   // Call each mixer input and signal an error.
   base::AutoLock auto_lock(lock_);
   for (const auto& cb : error_callbacks_)
     cb.Run();
 }
 
 }  // namespace media