Add empty residual echo detector.

webrtc/modules/audio_processing/residual_echo_detector.cc

+/*
+ *  Copyright (c) 2016 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/residual_echo_detector.h"
+
+#include "webrtc/modules/audio_processing/audio_buffer.h"
+
+namespace webrtc {
+
+ResidualEchoDetector::ResidualEchoDetector() = default;
+
+ResidualEchoDetector::~ResidualEchoDetector() = default;
+
+void ResidualEchoDetector::AnalyzeRenderAudio(
+    rtc::ArrayView<const float> render_audio) const {
+  // TODO(ivoc): Add implementation.
+}
+
+void ResidualEchoDetector::AnalyzeCaptureAudio(
+    rtc::ArrayView<const float> render_audio) {
+  // TODO(ivoc): Add implementation.
+}
+
+void ResidualEchoDetector::Initialize() {
+  // TODO(ivoc): Add implementation.
+}
+
+void ResidualEchoDetector::PackRenderAudioBuffer(
+    AudioBuffer* audio,
+    std::vector<float>* packed_buffer) {
+  RTC_DCHECK_GE(160u, audio->num_frames_per_band());
+
+  packed_buffer->clear();
+  packed_buffer->insert(packed_buffer->end(),
+                        audio->split_bands_const_f(0)[kBand0To8kHz],
+                        (audio->split_bands_const_f(0)[kBand0To8kHz] +
+                         audio->num_frames_per_band()));
+}
+
+float ResidualEchoDetector::get_echo_likelihood() const {
+  // TODO(ivoc): Add implementation.
+  return 0.0f;
+}
+
+}  // namespace webrtc