Introduce new interface for MediaInternals updates.

media/base/audio_logging.h

+// Copyright 2013 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_BASE_AUDIO_LOGGING_H_

[acolwell GONE FROM CHROMIUM, 2013/11/21 00:53:58]

It seems like media/audio would be a better home for this. Is there any reason
not to put it in there?

[DaleCurtis, 2013/11/21 01:18:30]

Done.

+#define MEDIA_BASE_AUDIO_LOGGING_H_
+
+#include <string>
+
+#include "base/memory/scoped_ptr.h"
+
+namespace media {
+class AudioParameters;

[acolwell GONE FROM CHROMIUM, 2013/11/21 00:53:58]

nit: move this down into the media namespace below.

[DaleCurtis, 2013/11/21 01:18:30]

Done.

+}
+
+namespace media {
+
+// AudioLog logs state information about an active audio component.  Each method
+// takes a |component_id|, a monotonically increasing integer, along with method

[acolwell GONE FROM CHROMIUM, 2013/11/21 00:53:58]

nit: Why is the monotonically increasing characteristic of component_id
discussed here? It seems like it is up to the AudioLog user to determine how it
wants to assign ID's to components. Are component_id's expected to be globally
unique?

[DaleCurtis, 2013/11/21 01:18:30]

It'd be nice if they were, but you're right that's up to the client.

+// specific information.  Its methods are safe to call from any thread.
+class AudioLog {
+ public:
+  // Called when an audio component is created.  |params| are the parameters of
+  // the created stream.  |input_device_id| and |output_device_id| are the
+  // respective device ids for input and output.  Either one or both may be
+  // specified.
+  virtual void OnCreated(int component_id,
+                         const media::AudioParameters& params,
+                         const std::string& input_device_id,
+                         const std::string& output_device_id) = 0;
+
+  // Called when an audio component is started, generally this is synonymous
+  // with "playing."
+  virtual void OnStarted(int component_id) = 0;
+
+  // Called when an audio component is stopped, generally this is synonymous
+  // with "paused."
+  virtual void OnStopped(int component_id) = 0;
+
+  // Called when an audio component is deleted, generally this is synonymous
+  // with "closed."
+  virtual void OnDeleted(int component_id) = 0;
+
+  // Called when an audio component changes volume.  |volume| is the new volume.
+  virtual void OnSetVolume(int component_id, double volume) = 0;
+
+ protected:
+  virtual ~AudioLog() {}
+};
+
+// AudioLogDispenser dispenses AudioLog instances to owning classes for tracking
+// AudioComponent behavior.  All AudioComponents have the concept of an owning
+// class:
+//
+//    - AudioInputRendererHost for AudioInputController
+//    - AudioRendererHost for AudioOutputController
+//    - AudioOutputDispatcherImpl for AudioOutputStream
+//
+// Each of these owning classes may own multiple instances of each component, as
+// such each AudioLog supports logging for multiple instances.
+class AudioLogDispenser {

[acolwell GONE FROM CHROMIUM, 2013/11/21 00:53:58]

nit: s/Dispenser/Factory since this appears to be a factory pattern and
dispenser is not a term used in any object names in the codebase.

[DaleCurtis, 2013/11/21 01:18:30]

Done.

+ public:
+  enum AudioComponent {
+    // Input controllers have a 1:1 mapping with streams, so there's no need to
+    // track both controllers and streams.
+    AUDIO_INPUT_CONTROLLER,
+    // Output controllers may or may not be backed by an active stream, so we
+    // need to track both controllers and streams.
+    AUDIO_OUTPUT_CONTROLLER,
+    AUDIO_OUTPUT_STREAM,
+  };
+
+  // Create a new AudioLog object for tracking the behavior for one or more
+  // instances of the given component.  Each instance of an "owning" class must
+  // create its own AudioLog.
+  virtual scoped_ptr<AudioLog> CreateAudioLog(AudioComponent component) = 0;
+
+ protected:
+  virtual ~AudioLogDispenser() {}
+};
+
+} // namespace media
+
+#endif  // MEDIA_BASE_AUDIO_LOGGING_H_