Update audio_processing module

Corresponds to upstream commit 524e9b043e7e86fd72353b987c9d5f6a1ebf83e1

Update notes:

 * Pull in third party license file

 * Replace .gypi files with BUILD.gn to keep track of what changes
   upstream

 * Bunch of new filse pulled in as dependencies

 * Won't build yet due to changes needed on top of these

webrtc/common_audio/real_fourier_openmax.h

@@ -0,0 +1,44 @@
+/*
+ *  Copyright (c) 2015 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_COMMON_AUDIO_REAL_FOURIER_OPENMAX_H_
+#define WEBRTC_COMMON_AUDIO_REAL_FOURIER_OPENMAX_H_
+
+#include <complex>
+
+#include "webrtc/common_audio/real_fourier.h"
+
+namespace webrtc {
+
+class RealFourierOpenmax : public RealFourier {
+ public:
+  explicit RealFourierOpenmax(int fft_order);
+  ~RealFourierOpenmax() override;
+
+  void Forward(const float* src, std::complex<float>* dest) const override;
+  void Inverse(const std::complex<float>* src, float* dest) const override;
+
+  int order() const override {
+    return order_;
+  }
+
+ private:
+  // Basically a forward declare of OMXFFTSpec_R_F32. To get rid of the
+  // dependency on openmax.
+  typedef void OMXFFTSpec_R_F32_;
+  const int order_;
+
+  OMXFFTSpec_R_F32_* const omx_spec_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_COMMON_AUDIO_REAL_FOURIER_OPENMAX_H_
+