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/resampler/push_sinc_resampler.cc

@@ -0,0 +1,103 @@
+/*
+ *  Copyright (c) 2013 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 "webrtc/common_audio/resampler/push_sinc_resampler.h"
+
+#include <cstring>
+
+#include "webrtc/base/checks.h"
+#include "webrtc/common_audio/include/audio_util.h"
+
+namespace webrtc {
+
+PushSincResampler::PushSincResampler(size_t source_frames,
+                                     size_t destination_frames)
+    : resampler_(new SincResampler(source_frames * 1.0 / destination_frames,
+                                   source_frames,
+                                   this)),
+      source_ptr_(nullptr),
+      source_ptr_int_(nullptr),
+      destination_frames_(destination_frames),
+      first_pass_(true),
+      source_available_(0) {}
+
+PushSincResampler::~PushSincResampler() {
+}
+
+size_t PushSincResampler::Resample(const int16_t* source,
+                                   size_t source_length,
+                                   int16_t* destination,
+                                   size_t destination_capacity) {
+  if (!float_buffer_.get())
+    float_buffer_.reset(new float[destination_frames_]);
+
+  source_ptr_int_ = source;
+  // Pass nullptr as the float source to have Run() read from the int16 source.
+  Resample(nullptr, source_length, float_buffer_.get(), destination_frames_);
+  FloatS16ToS16(float_buffer_.get(), destination_frames_, destination);
+  source_ptr_int_ = nullptr;
+  return destination_frames_;
+}
+
+size_t PushSincResampler::Resample(const float* source,
+                                   size_t source_length,
+                                   float* destination,
+                                   size_t destination_capacity) {
+  RTC_CHECK_EQ(source_length, resampler_->request_frames());
+  RTC_CHECK_GE(destination_capacity, destination_frames_);
+  // Cache the source pointer. Calling Resample() will immediately trigger
+  // the Run() callback whereupon we provide the cached value.
+  source_ptr_ = source;
+  source_available_ = source_length;
+
+  // On the first pass, we call Resample() twice. During the first call, we
+  // provide dummy input and discard the output. This is done to prime the
+  // SincResampler buffer with the correct delay (half the kernel size), thereby
+  // ensuring that all later Resample() calls will only result in one input
+  // request through Run().
+  //
+  // If this wasn't done, SincResampler would call Run() twice on the first
+  // pass, and we'd have to introduce an entire |source_frames| of delay, rather
+  // than the minimum half kernel.
+  //
+  // It works out that ChunkSize() is exactly the amount of output we need to
+  // request in order to prime the buffer with a single Run() request for
+  // |source_frames|.
+  if (first_pass_)
+    resampler_->Resample(resampler_->ChunkSize(), destination);
+
+  resampler_->Resample(destination_frames_, destination);
+  source_ptr_ = nullptr;
+  return destination_frames_;
+}
+
+void PushSincResampler::Run(size_t frames, float* destination) {
+  // Ensure we are only asked for the available samples. This would fail if
+  // Run() was triggered more than once per Resample() call.
+  RTC_CHECK_EQ(source_available_, frames);
+
+  if (first_pass_) {
+    // Provide dummy input on the first pass, the output of which will be
+    // discarded, as described in Resample().
+    std::memset(destination, 0, frames * sizeof(*destination));
+    first_pass_ = false;
+    return;
+  }
+
+  if (source_ptr_) {
+    std::memcpy(destination, source_ptr_, frames * sizeof(*destination));
+  } else {
+    for (size_t i = 0; i < frames; ++i)
+      destination[i] = static_cast<float>(source_ptr_int_[i]);
+  }
+  source_available_ -= frames;
+}
+
+}  // namespace webrtc