Added a perf test for the residual echo detector.

webrtc/modules/audio_processing/test/performance_timer.h

Index: webrtc/modules/audio_processing/test/performance_timer.h
diff --git a/webrtc/modules/audio_processing/test/performance_timer.h b/webrtc/modules/audio_processing/test/performance_timer.h
new file mode 100644
index 0000000000000000000000000000000000000000..5921fae07011a16aa8d0a83be8ed92fbb78a4c76
--- /dev/null
+++ b/webrtc/modules/audio_processing/test/performance_timer.h
@@ -0,0 +1,42 @@
+/*
+ *  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_TEST_PERFORMANCE_TIMER_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_TEST_PERFORMANCE_TIMER_H_
+
+#include <vector>
+
+#include "webrtc/base/optional.h"
+#include "webrtc/system_wrappers/include/clock.h"
+
+namespace webrtc {
+namespace test {
+
+class PerformanceTimer {
+ public:
+  explicit PerformanceTimer(int num_frames_to_process);
+  ~PerformanceTimer();
+
+  void StartTimer();
+  void StopTimer();
+
+  double GetDurationAverage() const;
+  double GetDurationStandardDeviation() const;
+
+ private:
+  webrtc::Clock* clock_;
+  rtc::Optional<int64_t> start_timestamp_us_;
+  std::vector<int64_t> timestamps_us_;
+};
+
+}  // namespace test
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_TEST_PERFORMANCE_TIMER_H_