Adding second layer of the echo canceller 3 functionality.

webrtc/modules/audio_processing/aec3/echo_path_delay_estimator.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/aec3/echo_path_delay_estimator.h"
+
+#include "webrtc/base/checks.h"
+#include "webrtc/modules/audio_processing/aec3/aec3_constants.h"
+#include "webrtc/modules/audio_processing/logging/apm_data_dumper.h"
+
+namespace webrtc {
+
+// TODO(peah): Add functionality.
+EchoPathDelayEstimator::EchoPathDelayEstimator(ApmDataDumper* data_dumper,
+                                               int sample_rate_hz) {
+  RTC_DCHECK(data_dumper);
+  RTC_DCHECK(sample_rate_hz == 8000 || sample_rate_hz == 16000 ||
+             sample_rate_hz == 32000 || sample_rate_hz == 48000);
+}
+
+EchoPathDelayEstimator::~EchoPathDelayEstimator() = default;
+
+// TODO(peah): Add functionality.
+rtc::Optional<size_t> EchoPathDelayEstimator::EstimateDelay(
+    rtc::ArrayView<const float> render,
+    rtc::ArrayView<const float> capture) {
+  RTC_DCHECK_EQ(render.size(), kBlockSize);
+  RTC_DCHECK_EQ(capture.size(), kBlockSize);
+  return rtc::Optional<size_t>();
+}
+
+}  // namespace webrtc