Switch Speech Recognition to asynchronous callback-based AudioManager interactions.

media/audio/audio_system_impl.cc

Index: media/audio/audio_system_impl.cc
diff --git a/media/audio/audio_system_impl.cc b/media/audio/audio_system_impl.cc
new file mode 100644
index 0000000000000000000000000000000000000000..35558bb165ece4af789a38e7cb4b11b1eb810560
--- /dev/null
+++ b/media/audio/audio_system_impl.cc
@@ -0,0 +1,70 @@
+// Copyright 2017 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/audio/audio_system_impl.h"
+
+#include "base/memory/ptr_util.h"
+#include "base/single_thread_task_runner.h"
+#include "base/task_runner_util.h"
+#include "media/audio/audio_manager.h"
+
+// Using base::Unretained for |audio_manager_| is safe since it is deleted after
+// its task runner, and AudioSystemImpl is deleted on the UI thread after the IO
+// thread has been stopped and before |audio_manager_| deletion is scheduled.
+namespace media {
+
+namespace {
+
+AudioParameters GetInputParametersOnDeviceThread(AudioManager* audio_manager,
+                                                 const std::string& device_id) {
+  DCHECK(audio_manager->GetTaskRunner()->BelongsToCurrentThread());
+
+  // TODO(olka) : remove this when AudioManager::GetInputStreamParameters()

[tommi (sloooow) - chröme, 2017/02/05 20:14:54]

nit: TODO(foo):

[o1ka, 2017/02/06 12:06:08]

Done.

+  // works this way on all the platforms.
+  if (!audio_manager->HasAudioInputDevices())
+    return AudioParameters();
+
+  return audio_manager->GetInputStreamParameters(device_id);
+}
+
+}  // namespace
+
+AudioSystemImpl::AudioSystemImpl(AudioManager* audio_manager)
+    : audio_manager_(audio_manager) {
+  DCHECK(audio_manager_);
+}
+
+AudioSystemImpl::~AudioSystemImpl() {}
+
+// static
+std::unique_ptr<AudioSystem> AudioSystemImpl::Create(
+    AudioManager* audio_manager) {
+  return base::WrapUnique(new AudioSystemImpl(audio_manager));
+}
+
+base::SingleThreadTaskRunner* AudioSystemImpl::GetTaskRunner() const {
+  return audio_manager_->GetTaskRunner();
+}
+
+void AudioSystemImpl::GetInputStreamParameters(

[tommi (sloooow) - chröme, 2017/02/05 20:14:54]

is it the intent that this method can be called on any thread?

[o1ka, 2017/02/06 12:06:08]

Yes, it can be called from UI and IO threads, and UI==audio thread on Mac.
I removed GetTaskRunner() from the interface for now. When/if somebody needs to
post AudioSystem calls to the audio thread, we'll need to re-conciser
AudioSystem lifetime, since now AudioSystem is deleted on IO thread and the
audio thread (and its tasks) outlives AudioSystem (this concern is not
applicable in Mac case).

+    const std::string& device_id,
+    OnAudioParamsCallback on_params_cb) {
+  if (GetTaskRunner()->BelongsToCurrentThread()) {
+    GetTaskRunner()->PostTask(
+        FROM_HERE, base::Bind(on_params_cb, GetInputParametersOnDeviceThread(
+                                                audio_manager_, device_id)));
+    return;
+  }
+  base::PostTaskAndReplyWithResult(
+      GetTaskRunner(), FROM_HERE,
+      base::Bind(&GetInputParametersOnDeviceThread,
+                 base::Unretained(audio_manager_), device_id),
+      std::move(on_params_cb));
+}
+
+AudioManager* AudioSystemImpl::GetAudioManager() {
+  return audio_manager_;
+}
+
+}  // namespace media