Bump to WebRTC M120 release

Some API deprecation -- ExperimentalAgc and ExperimentalNs are gone.
We're continuing to carry iSAC even though it's gone upstream, but maybe
we'll want to drop that soon.

webrtc/modules/audio_processing/agc2/saturation_protector_buffer.cc

@@ -0,0 +1,77 @@
+/*
+ *  Copyright (c) 2021 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 "modules/audio_processing/agc2/saturation_protector_buffer.h"
+
+#include "rtc_base/checks.h"
+#include "rtc_base/numerics/safe_compare.h"
+
+namespace webrtc {
+
+SaturationProtectorBuffer::SaturationProtectorBuffer() = default;
+
+SaturationProtectorBuffer::~SaturationProtectorBuffer() = default;
+
+bool SaturationProtectorBuffer::operator==(
+    const SaturationProtectorBuffer& b) const {
+  RTC_DCHECK_LE(size_, buffer_.size());
+  RTC_DCHECK_LE(b.size_, b.buffer_.size());
+  if (size_ != b.size_) {
+    return false;
+  }
+  for (int i = 0, i0 = FrontIndex(), i1 = b.FrontIndex(); i < size_;
+       ++i, ++i0, ++i1) {
+    if (buffer_[i0 % buffer_.size()] != b.buffer_[i1 % b.buffer_.size()]) {
+      return false;
+    }
+  }
+  return true;
+}
+
+int SaturationProtectorBuffer::Capacity() const {
+  return buffer_.size();
+}
+
+int SaturationProtectorBuffer::Size() const {
+  return size_;
+}
+
+void SaturationProtectorBuffer::Reset() {
+  next_ = 0;
+  size_ = 0;
+}
+
+void SaturationProtectorBuffer::PushBack(float v) {
+  RTC_DCHECK_GE(next_, 0);
+  RTC_DCHECK_GE(size_, 0);
+  RTC_DCHECK_LT(next_, buffer_.size());
+  RTC_DCHECK_LE(size_, buffer_.size());
+  buffer_[next_++] = v;
+  if (rtc::SafeEq(next_, buffer_.size())) {
+    next_ = 0;
+  }
+  if (rtc::SafeLt(size_, buffer_.size())) {
+    size_++;
+  }
+}
+
+absl::optional<float> SaturationProtectorBuffer::Front() const {
+  if (size_ == 0) {
+    return absl::nullopt;
+  }
+  RTC_DCHECK_LT(FrontIndex(), buffer_.size());
+  return buffer_[FrontIndex()];
+}
+
+int SaturationProtectorBuffer::FrontIndex() const {
+  return rtc::SafeEq(size_, buffer_.size()) ? next_ : 0;
+}
+
+}  // namespace webrtc