Probing: Add support for exponential startup probing

webrtc/modules/congestion_controller/delay_based_bwe_unittest_helper.cc

Index: webrtc/modules/congestion_controller/delay_based_bwe_unittest_helper.cc
diff --git a/webrtc/modules/congestion_controller/delay_based_bwe_unittest_helper.cc b/webrtc/modules/congestion_controller/delay_based_bwe_unittest_helper.cc
index 0ed7816e5047d38fc03e65fecd28f63662000555..4a9cf04f075df133b3563f1ded111f450569c65b 100644
--- a/webrtc/modules/congestion_controller/delay_based_bwe_unittest_helper.cc
+++ b/webrtc/modules/congestion_controller/delay_based_bwe_unittest_helper.cc
@@ -148,13 +148,13 @@ int64_t StreamGenerator::GenerateFrame(std::vector<PacketInfo>* packets,
 }
 }  // 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() {}