Move AudioDecoder and related stuff to the api/ directory

webrtc/api/audio_codecs/audio_format.h

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#ifndef WEBRTC_MODULES_AUDIO_CODING_CODECS_AUDIO_FORMAT_H_
-#define WEBRTC_MODULES_AUDIO_CODING_CODECS_AUDIO_FORMAT_H_
+#ifndef WEBRTC_API_AUDIO_CODECS_AUDIO_FORMAT_H_
+#define WEBRTC_API_AUDIO_CODECS_AUDIO_FORMAT_H_
 
 #include <map>
 #include <ostream>
 #include <string>
 #include <utility>
 
 namespace webrtc {
 
 // SDP specification for a single audio codec.
 // NOTE: This class is still under development and may change without notice.
@@ skipping 40 matching lines @@
 //   AudioCodecSpec spec({"format", 8000, 1});
 //   spec.allow_comfort_noise = true;
 //   spec.future_flag_b = true;
 //   spec.future_flag_c = true;
 struct AudioCodecSpec {
   explicit AudioCodecSpec(const SdpAudioFormat& format);
   explicit AudioCodecSpec(SdpAudioFormat&& format);
   ~AudioCodecSpec() = default;
 
   SdpAudioFormat format;
-  bool allow_comfort_noise = true;    // This codec can be used with an external
-                                      // comfort noise generator.
+  bool allow_comfort_noise = true;  // This codec can be used with an external
+                                    // comfort noise generator.
   bool supports_network_adaption = false;  // This codec can adapt to varying
                                            // network conditions.
 };
 
 }  // namespace webrtc
 
-#endif  // WEBRTC_MODULES_AUDIO_CODING_CODECS_AUDIO_FORMAT_H_
+#endif  // WEBRTC_API_AUDIO_CODECS_AUDIO_FORMAT_H_