Removes all const Clock*.

This prepares for making the Clock interface fully mutable.

Calls to the time functions in Clock can have side effects in some
circumstances. It's also questionable if it's a good idea to allow
repeated calls to a const method return different values without
any changed to the class instance.

Bug: webrtc:9883
Change-Id: I96fb9230705f7c80a4c0702132fd9dc73899fc5e
Reviewed-on: https://webrtc-review.googlesource.com/c/120347
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26467}
diff --git a/modules/bitrate_controller/bitrate_controller_impl.h b/modules/bitrate_controller/bitrate_controller_impl.h
index 5448c17..28dcc03 100644
--- a/modules/bitrate_controller/bitrate_controller_impl.h
+++ b/modules/bitrate_controller/bitrate_controller_impl.h
@@ -32,7 +32,7 @@
  public:
   // TODO(perkj): BitrateObserver has been deprecated and is not used in WebRTC.
   // |observer| is left for project that is not yet updated.
-  BitrateControllerImpl(const Clock* clock,
+  BitrateControllerImpl(Clock* clock,
                         BitrateObserver* observer,
                         RtcEventLog* event_log);
   virtual ~BitrateControllerImpl() {}
@@ -83,7 +83,7 @@
                         int64_t rtt) RTC_EXCLUSIVE_LOCKS_REQUIRED(critsect_);
 
   // Used by process thread.
-  const Clock* const clock_;
+  Clock* const clock_;
   BitrateObserver* const observer_;
   int64_t last_bitrate_update_ms_;
   RtcEventLog* const event_log_;