Moved AudioUtil static functions to AudioManager interfaces

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 102 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;
 
+  // Returns the default output hardware audio parameters for opening output
+  // streams. If the users inject a valid |input_params|, each AudioManager
+  // will decide if they should return the values from |input_params| or the
+  // default hardware values. If the |input_params| is invalid, it will simply
+  // return the default hardware audio parameters.
+  virtual AudioParameters GetDefaultOutputStreamParameters(

[Chris Rogers, 2013/03/04 01:04:11]

It would be good to have another version of this method taking no
|input_params|.  This would just be a convenience method so clients don't have
to pass in a "bogus" AudioParameter value just to get the default values. 
Several places in this CL have to pass in these empty "bogus" AudioParameters
which seems a bit clunky.

This convenience method wouldn't need to be implemented for each AudioManager
sub-class of course.

[no longer working on chromium, 2013/03/04 14:55:04]

I agree that is a bit clunky to force the clients to inject an empty
AudioParameters object. But adding one overloading method to the interface does
not seem suitable for AudioManager interface.
Lets take one step back instead.
GetDefaultOutputStreamParameters() is the interface to clients outside media.
GetDefaultOutputStreamParameters(const AudioParameters& input_params) is only
called by AudioManagerBase.
We want one implementation but two interfaces.

After talking to Tommi, I would suggest fallback to
GetDefaultOutputStreamParameters() in AudioManager, and add back one
GetPreferredOutputStreamParameters(const AudioParameters& input_params) to
AudioManagerBase.
The implementation of GetDefaultOutputStreamParameters() is in AudioManageBase,
which calls GetPreferredOutputStreamParameters(input_params), and DO NOT each
AudioManager to implement their own version.
Instead, each AudioManager should put the implementation in
GetPreferredOutputStreamParameters(const AudioParameters& input_params).

Chris and Dale, how do you think here? I uploaded a new version of code to
demonstrate the idea. Hope this version looks better.

+      const AudioParameters& input_params) = 0;
+
+  // Returns the input hardware audio parameters of the specific device
+  // for opening input streams.
+  virtual AudioParameters GetInputStreamParameters(
+      const std::string& device_id) = 0;
+
  protected:
   AudioManager();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AudioManager);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_MANAGER_H_