Add an ALSA output to the motown audio server.

services/media/audio/audio_output_manager.cc

 // Copyright 2015 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 <string>
 
 #include "services/media/audio/audio_output.h"
 #include "services/media/audio/audio_output_manager.h"
 #include "services/media/audio/audio_server_impl.h"
 #include "services/media/audio/audio_track_to_output_link.h"
 #include "services/media/audio/platform/generic/throttle_output.h"
 
 namespace mojo {
 namespace media {
 namespace audio {
 
 static constexpr size_t  THREAD_POOL_SZ = 2;
 static const std::string THREAD_PREFIX("AudioMixer");
 
+// TODO(johngro): This needs to be replaced with a proper HAL
+extern AudioOutputPtr CreateDefaultAlsaOutput(AudioOutputManager* manager);
+
 AudioOutputManager::AudioOutputManager(AudioServerImpl* server)
   : server_(server) {
 }
 
 AudioOutputManager::~AudioOutputManager() {
   Shutdown();
   DCHECK_EQ(outputs_.size(), 0u);
   DCHECK(!thread_pool_);
 }
 
 MediaResult AudioOutputManager::Init() {
   // Step #1: Initialize the mixing thread pool.
   //
   // TODO(johngro): make the thread pool size proportional to the maximum
   // number of cores available in the system.
   //
   // TODO(johngro): make sure that the threads are executed at an elevated
   // priority, not the default priority.
   thread_pool_ = new base::SequencedWorkerPool(THREAD_POOL_SZ, THREAD_PREFIX);
 
   // Step #2: Instantiate all of the built-in audio output devices.
   //
   // TODO(johngro): Come up with a better way of doing this based on our
   // platform.  Right now, we just create some hardcoded default outputs and
   // leave it at that.
   outputs_.emplace(audio::ThrottleOutput::New(this));
+  {
+    AudioOutputPtr alsa = CreateDefaultAlsaOutput(this);
+    if (alsa) { outputs_.emplace(alsa); }
+  }
 
   // Step #3: Being monitoring for plug/unplug events for pluggable audio
   // output devices.
   //
   // TODO(johngro): Implement step #3.  Right now, the details are behind
   // hot-plug monitoring are TBD, so the feature is not implemented.
 
   // Step #4: Attempt to initialize each of the audio outputs we have created,
   // then kick off the callback engine for each of them.
   for (auto iter = outputs_.begin(); iter != outputs_.end(); ) {
@@ skipping 85 matching lines @@
 void AudioOutputManager::ScheduleMessageLoopTask(
     const tracked_objects::Location& from_here,
     const base::Closure& task) {
   DCHECK(server_);
   server_->ScheduleMessageLoopTask(from_here, task);
 }
 
 }  // namespace audio
 }  // namespace media
 }  // namespace mojo