NetEq: Fix a bug in DelayPeakDetector causing asserts to trigger

webrtc/modules/audio_coding/neteq/delay_peak_detector_unittest.cc

 /*
  *  Copyright (c) 2012 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.
  */
 
@@ skipping 104 matching lines @@
       int iat_packets = (arrival_times_ms[next] - arrival_times_ms[next - 1]) /
           kPacketSizeMs;
       const int kTargetBufferLevel = 2;  // Define peaks to be iat > 4.
       EXPECT_FALSE(detector.Update(iat_packets, kTargetBufferLevel));
       ++next;
     }
     tick_timer.Increment();
     time += 10;  // Increase time 10 ms.
   }
 }
+
+// In situations with reordered packets, the DelayPeakDetector may be updated
+// back-to-back (i.e., without the tick_timer moving) but still with non-zero
+// inter-arrival time. This test is to make sure that this does not cause
+// problems.
+TEST(DelayPeakDetector, ZeroDistancePeaks) {
+  TickTimer tick_timer;
+  DelayPeakDetector detector(&tick_timer);
+  const int kPacketSizeMs = 30;
+  detector.SetPacketAudioLength(kPacketSizeMs);
+
+  const int kTargetBufferLevel = 2;  // Define peaks to be iat > 4.
+  const int kInterArrivalTime = 3 * kTargetBufferLevel;  // Will trigger a peak.
+  EXPECT_FALSE(detector.Update(kInterArrivalTime, kTargetBufferLevel));
+  EXPECT_FALSE(detector.Update(kInterArrivalTime, kTargetBufferLevel));
+  EXPECT_FALSE(detector.Update(kInterArrivalTime, kTargetBufferLevel));
+}
+
 }  // namespace webrtc