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

media/audio/audio_manager.h

Index: media/audio/audio_manager.h
diff --git a/media/audio/audio_manager.h b/media/audio/audio_manager.h
index 915308ef77d89cfea1470ee0b1696d44b5b94e12..35bb586ba13229f084279f9e06e7c1f79af4e787 100644
--- a/media/audio/audio_manager.h
+++ b/media/audio/audio_manager.h
@@ -145,6 +145,21 @@ class MEDIA_EXPORT AudioManager {
   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