Update the BWE when the network route changes.

webrtc/modules/congestion_controller/congestion_controller_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.
  */
 
@@ skipping 106 matching lines @@
   EXPECT_CALL(observer_, OnNetworkChanged(0, _, _));
   controller_->SignalNetworkState(kNetworkDown);
 
   EXPECT_CALL(observer_, OnNetworkChanged(kInitialBitrateBps, _, _));
   controller_->SignalNetworkState(kNetworkUp);
 
   EXPECT_CALL(observer_, OnNetworkChanged(0, _, _));
   controller_->SignalNetworkState(kNetworkDown);
 }
 
+TEST_F(CongestionControllerTest, ResetBweBitrates) {
+  int new_bitrate = 200000;
+  EXPECT_CALL(observer_, OnNetworkChanged(new_bitrate, _, _));
+  EXPECT_CALL(*pacer_, SetEstimatedBitrate(new_bitrate));
+  controller_->ResetBweBitrates(new_bitrate, -1, -1);
+
+  // If the bitrate is reset to -1, the new starting bitrate will be
+  // the minimum default bitrate 10000bps.
+  int min_default_bitrate = 10000;
+  EXPECT_CALL(observer_, OnNetworkChanged(min_default_bitrate, _, _));
+  EXPECT_CALL(*pacer_, SetEstimatedBitrate(min_default_bitrate));
+  controller_->ResetBweBitrates(-1, -1, -1);

[stefan-webrtc, 2016/05/30 06:47:03]

Is this a good behavior? Shouldn't we instead let it reset to the previous
bitrate? So essentially this call would be a no-op except for recreating BWE
objects.

[honghaiz3, 2016/05/31 16:58:03]

What do you mean by "previous bitrate"?
If you mean the bitrate right before we make the call, it then would be a no-op.

If you mean the bitrate before the last round of BWE, then we need to remember
the history. 
Plus the concept of "last round of BWE" is not clear to me.

What I attempt to do is to mimic the behavior of SetBweBitrates(-1, -1, -1) but
after creating a set
of BWE objects. So it would be the same as the state when the system starts with
SetBweBitrates(-1, -1, -1). 
WDYT? 

[stefan-webrtc, 2016/05/31 17:27:49]

I see.

I was thinking that if we want to reset only the max and min, then it would be
good to be able to pass in -1 as start bitrate. But I guess that is what it
already does, I may have just misunderstood.

+}
+
 TEST_F(CongestionControllerTest,
        SignalNetworkStateAndQueueIsFullAndEstimateChange) {
   // Send queue is full
   EXPECT_CALL(*pacer_, ExpectedQueueTimeMs())
       .WillRepeatedly(Return(PacedSender::kMaxQueueLengthMs + 1));
   EXPECT_CALL(observer_, OnNetworkChanged(0, _, _));
   controller_->Process();
 
   // Queue is full and network is down. Expect no bitrate change.
   controller_->SignalNetworkState(kNetworkDown);
@@ skipping 11 matching lines @@
 
   // Let the pacer not be full next time the controller checks.
   EXPECT_CALL(*pacer_, ExpectedQueueTimeMs())
       .WillOnce(Return(PacedSender::kMaxQueueLengthMs - 1));
   EXPECT_CALL(observer_, OnNetworkChanged(kInitialBitrateBps * 2, _, _));
   controller_->Process();
 }
 
 }  // namespace test
 }  // namespace webrtc