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

webrtc/modules/audio_processing/aec3/matched_filter_lag_aggregator.h

Index: webrtc/modules/audio_processing/aec3/matched_filter_lag_aggregator.h
diff --git a/webrtc/modules/audio_processing/aec3/matched_filter_lag_aggregator.h b/webrtc/modules/audio_processing/aec3/matched_filter_lag_aggregator.h
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+/*
+ *  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_MATCHED_FILTER_LAG_AGGREGATOR_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_MATCHED_FILTER_LAG_AGGREGATOR_H_
+
+#include <vector>
+
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/base/optional.h"
+#include "webrtc/modules/audio_processing/aec3/matched_filter.h"
+
+namespace webrtc {
+
+class ApmDataDumper;
+
+// Aggregates lag estimates produced by the MatchedFilter class into a single
+// reliable combined lag estimate.
+class MatchedFilterLagAggregator {
+ public:
+  MatchedFilterLagAggregator(ApmDataDumper* data_dumper,
+                             size_t num_lag_estimates);
+  ~MatchedFilterLagAggregator();
+
+  // Aggregates the provided lag estimates.
+  rtc::Optional<size_t> Aggregate(
+      rtc::ArrayView<const MatchedFilter::LagEstimate> lag_estimates);
+
+ private:
+  ApmDataDumper* const data_dumper_;
+  std::vector<size_t> lag_updates_in_a_row_;
+  size_t candidate_ = 0;
+  size_t candidate_counter_ = 0;
+
+  RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(MatchedFilterLagAggregator);
+};
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_MATCHED_FILTER_LAG_AGGREGATOR_H_