AGC2 as a new APM sub-module operating with hard-coded gain.

webrtc/modules/audio_processing/agc2/agc2_impl.cc

+/*
+ *  Copyright (c) 2017 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/modules/audio_processing/agc2/agc2_impl.h"
+
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+
+Agc2Impl::Agc2Impl(rtc::CriticalSection* crit)
+    : crit_(crit) {
+  RTC_CHECK(crit_);
+}
+
+Agc2Impl::~Agc2Impl() = default;
+
+bool Agc2Impl::Validate(const AudioProcessing::Config::Agc2& config) {
+  return true;
+}
+
+std::string Agc2Impl::ToString(const AudioProcessing::Config::Agc2& config) {
+  std::stringstream ss;
+  ss << "{"
+     << "enabled: " << (config.enabled ? "true" : "false") << "}";
+  return ss.str();
+}
+
+}  // namespace webrtc