Revert of Replace scoped_ptr with unique_ptr in webrtc/common_audio/

webrtc/common_audio/audio_converter.h

Index: webrtc/common_audio/audio_converter.h
diff --git a/webrtc/common_audio/audio_converter.h b/webrtc/common_audio/audio_converter.h
index 01dad4dfc89699976efd8b5e6925cf5d332725a0..c5f08c1d9b6471586e1e9dfc63d73886422d334f 100644
--- a/webrtc/common_audio/audio_converter.h
+++ b/webrtc/common_audio/audio_converter.h
@@ -11,9 +11,8 @@
 #ifndef WEBRTC_COMMON_AUDIO_AUDIO_CONVERTER_H_
 #define WEBRTC_COMMON_AUDIO_AUDIO_CONVERTER_H_
 
-#include <memory>
-
 #include "webrtc/base/constructormagic.h"
+#include "webrtc/base/scoped_ptr.h"
 
 namespace webrtc {
 
@@ -27,7 +26,7 @@
  public:
   // Returns a new AudioConverter, which will use the supplied format for its
   // lifetime. Caller is responsible for the memory.
-  static std::unique_ptr<AudioConverter> Create(size_t src_channels,
+  static rtc::scoped_ptr<AudioConverter> Create(size_t src_channels,
                                                 size_t src_frames,
                                                 size_t dst_channels,
                                                 size_t dst_frames);