Removes redundant starting rate.

Sine a starting rate field was added to the constraints struct. Having
it in the initial config separately is reduntant. To simplify the code,
the extra field is removed. This is a follow up on:
https://webrtc-review.googlesource.com/c/src/+/92624

Bug: webrtc:9586
Change-Id: I9b01b16b2fc4b8479e83b7e998308be2295e0325
Reviewed-on: https://webrtc-review.googlesource.com/96801
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24514}

api/transport/network_control.h

@@ -29,15 +29,13 @@ class TargetTransferRateObserver {
 // optional to use for a network controller implementation.
 struct NetworkControllerConfig {
   // The initial constraints to start with, these can be changed at any later
-  // time by calls to OnTargetRateConstraints.
+  // time by calls to OnTargetRateConstraints. Note that the starting rate
+  // has to be set initially to provide a starting state for the network
+  // controller, even though the field is marked as optional.
   TargetRateConstraints constraints;
   // Initial stream specific configuration, these are changed at any later time
   // by calls to OnStreamsConfig.
   StreamsConfig stream_based_config;
-  // The initial bandwidth estimate to base target rate on. This should be used
-  // as the basis for initial OnTargetTransferRate and OnPacerConfig callbacks.
-  // Note that starting rate is only provided on construction.
-  DataRate starting_bandwidth = DataRate::Infinity();
 };
 
 // NetworkControllerInterface is implemented by network controllers. A network

api/transport/network_types.h

@@ -45,6 +45,8 @@ struct TargetRateConstraints {
   Timestamp at_time = Timestamp::Infinity();
   absl::optional<DataRate> min_data_rate;
   absl::optional<DataRate> max_data_rate;
+  // The initial bandwidth estimate to base target rate on. This should be used
+  // as the basis for initial OnTargetTransferRate and OnPacerConfig callbacks.
   absl::optional<DataRate> starting_rate;
 };