Small refactoring of AudioProcessing use in channel.cc.

- Apply consistent naming.
- Use a scoped_ptr for rx_audioproc_.
- Remove now unnecessary AudioProcessing::Destroy().

R=bjornv@webrtc.org, xians@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2184007

git-svn-id: http://webrtc.googlecode.com/svn/trunk@4784 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/audio_processing/include/audio_processing.h

@@ -105,8 +105,7 @@ class VoiceDetection;
 // apm->Initialize();
 //
 // // Close the application...
-// AudioProcessing::Destroy(apm);
-// apm = NULL;
+// delete apm;
 //
 class AudioProcessing : public Module {
  public:
@@ -118,11 +117,6 @@ class AudioProcessing : public Module {
   static AudioProcessing* Create(int id);
   virtual ~AudioProcessing() {}
 
-  // TODO(andrew): remove this method. We now allow users to delete instances
-  // directly, useful for scoped_ptr.
-  // Destroys a |apm| instance.
-  static void Destroy(AudioProcessing* apm);
-
   // Initializes internal states, while retaining all user settings. This
   // should be called before beginning to process a new audio stream. However,
   // it is not necessary to call before processing the first stream after