Add empty residual echo detector.

webrtc/modules/audio_processing/residual_echo_detector.h

Index: webrtc/modules/audio_processing/residual_echo_detector.h
diff --git a/webrtc/modules/audio_processing/residual_echo_detector.h b/webrtc/modules/audio_processing/residual_echo_detector.h
new file mode 100644
index 0000000000000000000000000000000000000000..723371c7ce68c57756420ed7b1cf7aa21a31e2ae
--- /dev/null
+++ b/webrtc/modules/audio_processing/residual_echo_detector.h
@@ -0,0 +1,47 @@
+/*
+ *  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.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_PROCESSING_RESIDUAL_ECHO_DETECTOR_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_RESIDUAL_ECHO_DETECTOR_H_
+
+#include <memory>
+#include <vector>
+
+#include "webrtc/base/array_view.h"
+
+namespace webrtc {
+
+class AudioBuffer;
+class EchoDetector;
+
+class ResidualEchoDetector {
+ public:
+  ResidualEchoDetector();
+  ~ResidualEchoDetector();
+
+  // This function should be called while holding the render lock.
+  void AnalyzeRenderAudio(rtc::ArrayView<const float> render_audio) const;
+
+  // This function should be called while holding the capture lock.
+  void AnalyzeCaptureAudio(rtc::ArrayView<const float> capture_audio);
+
+  // This function should be called while holding the capture lock.
+  void Initialize();
+
+  static void PackRenderAudioBuffer(AudioBuffer* audio,
+                                    std::vector<float>* packed_buffer);
+
+  // This function should be called while holding the capture lock.
+  float get_echo_likelihood() const;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_RESIDUAL_ECHO_DETECTOR_H_