Relanding "Pass time constant to bwe smoothing filter."

webrtc/modules/congestion_controller/include/congestion_controller.h

Index: webrtc/modules/congestion_controller/include/congestion_controller.h
diff --git a/webrtc/modules/congestion_controller/include/congestion_controller.h b/webrtc/modules/congestion_controller/include/congestion_controller.h
index ed37b9a4ce67dfcf55d250579c93c98561b571a8..f2bec76f2523c175b90577f24c72f3a1c56040c2 100644
--- a/webrtc/modules/congestion_controller/include/congestion_controller.h
+++ b/webrtc/modules/congestion_controller/include/congestion_controller.h
@@ -14,6 +14,7 @@
 #include <memory>
 
 #include "webrtc/base/constructormagic.h"
+#include "webrtc/base/deprecation.h"
 #include "webrtc/common_types.h"
 #include "webrtc/modules/congestion_controller/transport_feedback_adapter.h"
 #include "webrtc/modules/include/module.h"
@@ -46,9 +47,17 @@ class CongestionController : public CallStatsObserver, public Module {
   // packet headers and is measured in bits per second.
   class Observer {
    public:
+    // This is to be deprecated. Please use the one below instead.
+    RTC_DEPRECATED virtual void OnNetworkChanged(uint32_t bitrate_bps,
+                                                 uint8_t fraction_loss,
+                                                 int64_t rtt_ms) {}
+
+    // TODO(minyue): make this method pure virtual when all uses of the old API
+    // have been updated.
     virtual void OnNetworkChanged(uint32_t bitrate_bps,
                                   uint8_t fraction_loss,  // 0 - 255.
-                                  int64_t rtt_ms) = 0;
+                                  int64_t rtt_ms,
+                                  int64_t probing_interval_ms) {}
 
    protected:
     virtual ~Observer() {}