Move AudioDecoder and related stuff to the api/ directory

webrtc/modules/audio_coding/codecs/builtin_audio_decoder_factory_unittest.cc

 /*
  *  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.
  */
 
 #include <memory>
 
-#include "webrtc/modules/audio_coding/codecs/builtin_audio_decoder_factory.h"
+#include "webrtc/api/audio_codecs/builtin_audio_decoder_factory.h"
 #include "webrtc/test/gtest.h"
 
 namespace webrtc {
 
 TEST(AudioDecoderFactoryTest, CreateUnknownDecoder) {
   rtc::scoped_refptr<AudioDecoderFactory> adf =
       CreateBuiltinAudioDecoderFactory();
   ASSERT_TRUE(adf);
   EXPECT_FALSE(adf->MakeAudioDecoder(SdpAudioFormat("rey", 8000, 1)));
 }
@@ skipping 101 matching lines @@
         const bool good = (hz == 48000 && channels == 2 &&
                            (stereo == "XX" || stereo == "0" || stereo == "1"));
         EXPECT_EQ(good, static_cast<bool>(adf->MakeAudioDecoder(SdpAudioFormat(
                             "opus", hz, channels, std::move(params)))));
       }
     }
   }
 }
 
 }  // namespace webrtc