Adding full initial version of delay estimation functionality in echo canceller 3

webrtc/modules/audio_processing/aec3/echo_path_delay_estimator.h

 /*
  *  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.
  */
 
 #ifndef WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_ECHO_PATH_DELAY_ESTIMATOR_H_
 #define WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_ECHO_PATH_DELAY_ESTIMATOR_H_
 
 #include <vector>
 
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/base/optional.h"
+#include "webrtc/modules/audio_processing/aec3/matched_filter.h"
+#include "webrtc/modules/audio_processing/aec3/matched_filter_lag_aggregator.h"
+#include "webrtc/modules/audio_processing/aec3/decimator_by_4.h"
 
 namespace webrtc {
 
 class ApmDataDumper;
 
+// Estimates the delay of the echo path.
 class EchoPathDelayEstimator {
  public:
-  EchoPathDelayEstimator(ApmDataDumper* data_dumper, int sample_rate_hz);
+  explicit EchoPathDelayEstimator(ApmDataDumper* data_dumper);
   ~EchoPathDelayEstimator();
+
+  // Produce a delay estimate if such is avaliable.
   rtc::Optional<size_t> EstimateDelay(rtc::ArrayView<const float> render,
                                       rtc::ArrayView<const float> capture);
 
  private:
+  ApmDataDumper* const data_dumper_;
+  DecimatorBy4 render_decimator_;
+  DecimatorBy4 capture_decimator_;
+  MatchedFilter matched_filter_;
+  MatchedFilterLagAggregator matched_filter_lag_aggregator_;
+
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(EchoPathDelayEstimator);
 };
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_ECHO_PATH_DELAY_ESTIMATOR_H_