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

webrtc/modules/audio_processing/aec3/echo_path_delay_estimator.h

Index: webrtc/modules/audio_processing/aec3/echo_path_delay_estimator.h
diff --git a/webrtc/modules/audio_processing/aec3/echo_path_delay_estimator.h b/webrtc/modules/audio_processing/aec3/echo_path_delay_estimator.h
index ae8ab4318e66a52ee84dddd743caa104b4b347de..bbe9a7c32a6719cd9fc0d610dd992fee113d1541 100644
--- a/webrtc/modules/audio_processing/aec3/echo_path_delay_estimator.h
+++ b/webrtc/modules/audio_processing/aec3/echo_path_delay_estimator.h
@@ -15,19 +15,31 @@
 
 #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