Improve logging related to start/stop and failure of audio input streams in Chrome

media/audio/audio_manager.h

 // 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.
 
 #ifndef MEDIA_AUDIO_AUDIO_MANAGER_H_
 #define MEDIA_AUDIO_AUDIO_MANAGER_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 127 matching lines @@
   // callback is to recreate the stream.
   class AudioDeviceListener {
    public:
     virtual void OnDeviceChange() = 0;
   };
 
   virtual void AddOutputDeviceChangeListener(AudioDeviceListener* listener) = 0;
   virtual void RemoveOutputDeviceChangeListener(
       AudioDeviceListener* listener) = 0;
 
+  // It is possible to register listeners for logging of important state
+  // changes. These are mainly intended for input streams and is used to track
+  // down issues related to failing captured audio (http://crbug.com/404884).
+  // The typical repsonse to receiving this callback is to add the information
+  // to some sort of log file.
+  // TODO(henrika): remove these when we have understood why audio is sometimes
+  // not captured as it should. See http://crbug.com/405449.
+  class StateChangeListener {
+   public:
+    virtual void OnStateChange(const std::string& state) = 0;

[tommi (sloooow) - chröme, 2014/08/26 11:42:31]

Having |state| be a string is not what I'd expect.  Should/can this be an enum?

If not then it sounds like this is more of a logging specific function.  Is it
only to be used for DLOGing stuff or is this for the webrtc log?
If the former, I'd like to avoid having an interface for it cause this is
stretching the architecture to include ad-hoc printf tracing for developers, but
if this is for the webrtc log, let's make that very clear... and if that's
really the case, I'm not sure it belongs in AudioManager :-/

[henrika (OOO until Aug 14), 2014/08/27 13:44:05]

Removed!

+  };
+
+  virtual void AddStateChangeListener(StateChangeListener* listener) = 0;
+  virtual void RemoveStateChangeListener(StateChangeListener* listener) = 0;
+
   // Returns the default output hardware audio parameters for opening output
   // streams. It is a convenience interface to
   // AudioManagerBase::GetPreferredOutputStreamParameters and each AudioManager
   // does not need their own implementation to this interface.
   // TODO(tommi): Remove this method and use GetOutputStreamParameteres instead.
   virtual AudioParameters GetDefaultOutputStreamParameters() = 0;
 
   // Returns the output hardware audio parameters for a specific output device.
   virtual AudioParameters GetOutputStreamParameters(
       const std::string& device_id) = 0;
@@ skipping 22 matching lines @@
  protected:
   AudioManager();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AudioManager);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_MANAGER_H_