Mark |Clock*| as |const Clock*| (for some CongestionController and BWE related modules)

webrtc/modules/congestion_controller/congestion_controller.cc

Index: webrtc/modules/congestion_controller/congestion_controller.cc
diff --git a/webrtc/modules/congestion_controller/congestion_controller.cc b/webrtc/modules/congestion_controller/congestion_controller.cc
index 6ed64a299d73799ef4781277eacdb0e8770a39d4..3c349399ce7f66307ebcc43d72d923f46c6ea75b 100644
--- a/webrtc/modules/congestion_controller/congestion_controller.cc
+++ b/webrtc/modules/congestion_controller/congestion_controller.cc
@@ -48,7 +48,7 @@ static void ClampBitrates(int* bitrate_bps,
 }  // namespace
 
 CongestionController::WrappingBitrateEstimator::WrappingBitrateEstimator(
-    RemoteBitrateObserver* observer, Clock* clock)
+    RemoteBitrateObserver* observer, const Clock* clock)
     : observer_(observer),
       clock_(clock),
       rbe_(new RemoteBitrateEstimatorSingleStream(observer_, clock_)),
@@ -137,7 +137,7 @@ void CongestionController::WrappingBitrateEstimator::PickEstimator() {
 }
 
 CongestionController::CongestionController(
-    Clock* clock,
+    const Clock* clock,
     Observer* observer,
     RemoteBitrateObserver* remote_bitrate_observer,
     RtcEventLog* event_log,
@@ -152,7 +152,7 @@ CongestionController::CongestionController(
 }
 
 CongestionController::CongestionController(
-    Clock* clock,
+    const Clock* clock,
     Observer* observer,
     RemoteBitrateObserver* remote_bitrate_observer,
     RtcEventLog* event_log,