audio_coding: remove "main" directory

This is the last piece of the old directory layout of the modules.

Duplicated header files are left in audio_coding/main/include until
downstream code is updated to the new location. They have pragma
warnings added to them and identical header guards as the new headers to avoid breaking things.

BUG=webrtc:5095
TESTED=Passing compile-trybots with --clobber flag:
git cl try --clobber --bot=win_compile_rel --bot=linux_compile_rel --bot=android_compile_rel --bot=mac_compile_rel --bot=ios_rel --bot=linux_gn_rel --bot=win_x64_gn_rel --bot=mac_x64_gn_rel --bot=android_gn_rel -m tryserver.webrtc
NOTRY=True
NOPRESUBMIT=True

Review URL: https://codereview.webrtc.org/1481493004

Cr-Commit-Position: refs/heads/master@{#10803}
diff --git a/webrtc/modules/audio_coding/test/PCMFile.h b/webrtc/modules/audio_coding/test/PCMFile.h
new file mode 100644
index 0000000..9365180
--- /dev/null
+++ b/webrtc/modules/audio_coding/test/PCMFile.h
@@ -0,0 +1,68 @@
+/*
+ *  Copyright (c) 2012 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_TEST_PCMFILE_H_
+#define WEBRTC_MODULES_AUDIO_CODING_TEST_PCMFILE_H_
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <string>
+
+#include "webrtc/modules/include/module_common_types.h"
+#include "webrtc/typedefs.h"
+
+namespace webrtc {
+
+class PCMFile {
+ public:
+  PCMFile();
+  PCMFile(uint32_t timestamp);
+  ~PCMFile() {
+    if (pcm_file_ != NULL) {
+      fclose(pcm_file_);
+    }
+  }
+
+  void Open(const std::string& filename, uint16_t frequency, const char* mode,
+            bool auto_rewind = false);
+
+  int32_t Read10MsData(AudioFrame& audio_frame);
+
+  void Write10MsData(int16_t *playout_buffer, size_t length_smpls);
+  void Write10MsData(AudioFrame& audio_frame);
+
+  uint16_t PayloadLength10Ms() const;
+  int32_t SamplingFrequency() const;
+  void Close();
+  bool EndOfFile() const {
+    return end_of_file_;
+  }
+  void Rewind();
+  static int16_t ChooseFile(std::string* file_name, int16_t max_len,
+                            uint16_t* frequency_hz);
+  bool Rewinded();
+  void SaveStereo(bool is_stereo = true);
+  void ReadStereo(bool is_stereo = true);
+ private:
+  FILE* pcm_file_;
+  uint16_t samples_10ms_;
+  int32_t frequency_;
+  bool end_of_file_;
+  bool auto_rewind_;
+  bool rewinded_;
+  uint32_t timestamp_;
+  bool read_stereo_;
+  bool save_stereo_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_CODING_TEST_PCMFILE_H_