Switching AudioInputDeviceManager from using AudioManager interface to AudioSystem one.

media/audio/audio_system.h

 // 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.
 
 #ifndef MEDIA_AUDIO_AUDIO_SYSTEM_H_
 #define MEDIA_AUDIO_AUDIO_SYSTEM_H_
 
 #include "base/callback.h"
+#include "base/memory/weak_ptr.h"
 #include "media/audio/audio_device_description.h"
 #include "media/base/audio_parameters.h"
 #include "media/base/media_export.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace media {
 class AudioManager;
 
 // Work in progress: Provides asynchronous interface to AudioManager. All the
 // AudioManager clients will be switched to it, in preparation for moving
 // to Mojo audio service.
 class MEDIA_EXPORT AudioSystem {
  public:
+  class OnAudioThreadDeleter {
+   public:
+    void operator()(const AudioSystem* instance) const;
+  };
+
+  using UniquePtr = std::unique_ptr<AudioSystem, OnAudioThreadDeleter>;
+
   // Replies are asynchronously sent from audio system thread to the thread the
   // call is issued on. Attention! Since audio system thread may outlive all the
   // others, callbacks must always be bound to weak pointers!
   using OnAudioParamsCallback = base::Callback<void(const AudioParameters&)>;
   using OnBoolCallback = base::Callback<void(bool)>;
   using OnDeviceDescriptionsCallback =
       base::Callback<void(AudioDeviceDescriptions)>;
+  using OnDeviceIdCallback = base::Callback<void(const std::string&)>;
 
+  // Must not be called on audio thread, since it outlives the global pointer.
   static AudioSystem* Get();
 
   virtual ~AudioSystem();
 
   // Callback may receive invalid parameters, it means the specified device is
   // not found. This is best-effort: valid parameters do not guarantee existance
   // of the device.
   // TODO(olka,tommi): fix all AudioManager implementations to return invalid
   // parameters if the device is not found.
   virtual void GetInputStreamParameters(
       const std::string& device_id,
       OnAudioParamsCallback on_params_cb) const = 0;
 
   // If media::AudioDeviceDescription::IsDefaultDevice(device_id) is true,
   // callback will receive the parameters of the default output device.
   // Callback may receive invalid parameters, it means the specified device is
   // not found. This is best-effort: valid parameters do not guarantee existance
   // of the device.
   // TODO(olka,tommi): fix all AudioManager implementations to return invalid
   // parameters if the device is not found.
   virtual void GetOutputStreamParameters(
       const std::string& device_id,
       OnAudioParamsCallback on_params_cb) const = 0;
 
   virtual void HasInputDevices(OnBoolCallback on_has_devices_cb) const = 0;
 
   // Replies with device descriptions of input audio devices if |for_input| is
   // true, and of output audio devices otherwise.
   virtual void GetDeviceDescriptions(
-      OnDeviceDescriptionsCallback on_descriptions_cp,
+      OnDeviceDescriptionsCallback on_descriptions_cb,
       bool for_input) = 0;
 
+  virtual void GetAssociatedOutputDeviceID(
+      const std::string& input_device_id,
+      OnDeviceIdCallback on_device_id_cb) = 0;
+
+  // To be used on audio thread only.

[DaleCurtis, 2017/03/22 19:08:34]

Sorry, this is bad practice, can you find another way to achieve what you're
trying to do here? We  try to avoid vending WeakPtrs to outside classes. Instead
lifetime needs to be managed such that this class outlives everything that
should all it.

+  // AudioSystem instance must be posted to its task runner in form of a weak
+  // pointer, since the task runner outlives it.
+  virtual base::WeakPtr<AudioSystem> GetWeakPtr() = 0;
+
   virtual base::SingleThreadTaskRunner* GetTaskRunner() const = 0;
 
   // Must not be used for anything but stream creation.
   virtual AudioManager* GetAudioManager() const = 0;
 
  protected:
   // Sets the global AudioSystem pointer to the specified non-null value.
   static void SetInstance(AudioSystem* audio_system);
 
   // Sets the global AudioSystem pointer to null if it equals the specified one.
   static void ClearInstance(const AudioSystem* audio_system);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_SYSTEM_H_