Switching MediaStreamManager from using AudioManager to AudioSystem

media/audio/audio_system.h

Index: media/audio/audio_system.h
diff --git a/media/audio/audio_system.h b/media/audio/audio_system.h
index 76319cc2eb75aa1f84c513f030ce9f6729c9e872..de05c69aff9472f5a91975199bb110810559d1f2 100644
--- a/media/audio/audio_system.h
+++ b/media/audio/audio_system.h
@@ -9,6 +9,10 @@
 #include "media/base/audio_parameters.h"
 #include "media/base/media_export.h"
 
+namespace base {
+class SingleThreadTaskRunner;
+}
+
 namespace media {
 class AudioManager;
 
@@ -17,7 +21,9 @@ class AudioManager;
 // to Mojo audio service.
 class MEDIA_EXPORT AudioSystem {
  public:
-  // Replies are asynchronously sent to the thread the call is issued on.
+  // 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)>;
 
@@ -47,6 +53,8 @@ class MEDIA_EXPORT AudioSystem {
 
   virtual void HasInputDevices(OnBoolCallback on_has_devices_cb) const = 0;
 
+  virtual base::SingleThreadTaskRunner* GetTaskRunner() const = 0;
+
   // Must not be used for anything but stream creation.
   virtual AudioManager* GetAudioManager() const = 0;