Probing: Add support for exponential startup probing

webrtc/modules/congestion_controller/delay_based_bwe_unittest_helper.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 "webrtc/modules/congestion_controller/delay_based_bwe_unittest_helper.h"
@@ skipping 130 matching lines @@
         std::max(time_now_us + required_network_time_us,
                  prev_arrival_time_us_ + required_network_time_us);
     packet.arrival_time_ms = prev_arrival_time_us_ / 1000;
     ++i;
   }
   it = std::min_element(streams_.begin(), streams_.end(), RtpStream::Compare);
   return std::max((*it)->next_rtp_time(), time_now_us);
 }
 }  // namespace test
 
+// TODO(isheriff): Tests need fixes before submit.
 DelayBasedBweTest::DelayBasedBweTest()
     : clock_(100000000),
       bitrate_observer_(new test::TestBitrateObserver),
-      bitrate_estimator_(new DelayBasedBwe(bitrate_observer_.get(), &clock_)),
-      stream_generator_(
-          new test::StreamGenerator(1e6,  // Capacity.
-                                    clock_.TimeInMicroseconds())),
+      bitrate_estimator_(new DelayBasedBwe(nullptr, &clock_)),
+      stream_generator_(new test::StreamGenerator(1e6,  // Capacity.
+                                                  clock_.TimeInMicroseconds())),
       arrival_time_offset_ms_(0) {}
 
 DelayBasedBweTest::~DelayBasedBweTest() {}
 
 void DelayBasedBweTest::AddDefaultStream() {
   stream_generator_->AddStream(new test::RtpStream(30, 3e5));
 }
 
 const uint32_t DelayBasedBweTest::kDefaultSsrc = 0;
 
@@ skipping 327 matching lines @@
                      sequence_number++, 1000);
     clock_.AdvanceTimeMilliseconds(2 * kFrameIntervalMs);
     send_time_ms += kFrameIntervalMs;
     bitrate_estimator_->Process();
   }
   uint32_t bitrate_after = 0;
   bitrate_estimator_->LatestEstimate(&ssrcs, &bitrate_after);
   EXPECT_LT(bitrate_after, bitrate_before);
 }
 }  // namespace webrtc