fix wrong implementation of AimdRateControl::TimeToReduceFurther.

webrtc/modules/remote_bitrate_estimator/aimd_rate_control_unittest.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 <memory>
@@ skipping 71 matching lines @@
 TEST(AimdRateControlTest, GetLastBitrateDecrease) {
   auto states = CreateAimdRateControlStates();
   constexpr int kBitrate = 300000;
   InitBitrate(states, kBitrate, states.simulated_clock->TimeInMilliseconds());
   UpdateRateControl(states, kBwOverusing, kBitrate - 2000,
                     states.simulated_clock->TimeInMilliseconds());
   EXPECT_EQ(rtc::Optional<int>(46700),
             states.aimd_rate_control->GetLastBitrateDecreaseBps());
 }
 
+TEST(AimdRateControlTest, OneRTTWithoutBitrateChangeWhenOverUsing) {
+  auto states = CreateAimdRateControlStates();
+  constexpr int kBitrate = 300000;
+  constexpr int64_t kRtt = 150;
+  InitBitrate(states, kBitrate, states.simulated_clock->TimeInMilliseconds());
+  UpdateRateControl(states, kBwOverusing, kBitrate - 2000,
+                    states.simulated_clock->TimeInMilliseconds());
+  states.aimd_rate_control->SetRtt(kRtt);
+  EXPECT_FALSE(states.aimd_rate_control->TimeToReduceFurther(
+               states.simulated_clock->TimeInMilliseconds(), kBitrate));
+  states.simulated_clock->AdvanceTimeMilliseconds(kRtt);
+  EXPECT_TRUE(states.aimd_rate_control->TimeToReduceFurther(
+              states.simulated_clock->TimeInMilliseconds(), kBitrate));
+}
+
+TEST(AimdRateControlTest, EstimatedAlreadyAchievedWhenOverUsing) {
+  auto states = CreateAimdRateControlStates();
+  constexpr int kBitrate = 300000;
+  constexpr int64_t kRtt = 150;
+  uint32_t bitrate;
+  InitBitrate(states, kBitrate, states.simulated_clock->TimeInMilliseconds());
+  UpdateRateControl(states, kBwOverusing, kBitrate - 2000,
+                    states.simulated_clock->TimeInMilliseconds());
+  states.aimd_rate_control->SetRtt(kRtt);
+  bitrate = states.aimd_rate_control->LatestEstimate();
+  EXPECT_FALSE(states.aimd_rate_control->TimeToReduceFurther(
+               states.simulated_clock->TimeInMilliseconds(), bitrate));
+  bitrate = static_cast<uint32_t>(0.95 * bitrate);
+  EXPECT_TRUE(states.aimd_rate_control->TimeToReduceFurther(
+              states.simulated_clock->TimeInMilliseconds(), bitrate));
+}
+
 }  // namespace webrtc