Enable configuring probes via field trial.

This CL adds a field trial that lets us control the size of the initial probes, how we grow the following probes and how big and frequent our ALR probes are.

Bug: webrtc:10394
Change-Id: I6c7783dfada9aaf55cd836dd8991bb7b8ca4993b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/126880
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Commit-Queue: Jonas Olsson <jonasolsson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27077}
diff --git a/modules/congestion_controller/goog_cc/probe_controller.h b/modules/congestion_controller/goog_cc/probe_controller.h
index f937987..d0efb27 100644
--- a/modules/congestion_controller/goog_cc/probe_controller.h
+++ b/modules/congestion_controller/goog_cc/probe_controller.h
@@ -21,12 +21,34 @@
 #include "api/transport/webrtc_key_value_config.h"
 #include "logging/rtc_event_log/rtc_event_log.h"
 #include "rtc_base/constructor_magic.h"
+#include "rtc_base/experiments/field_trial_parser.h"
 #include "rtc_base/system/unused.h"
 
 namespace webrtc {
 
 class Clock;
 
+struct ProbeControllerConfig {
+  explicit ProbeControllerConfig(const WebRtcKeyValueConfig* key_value_config);
+  ProbeControllerConfig(const ProbeControllerConfig&);
+  ProbeControllerConfig& operator=(const ProbeControllerConfig&) = default;
+  ~ProbeControllerConfig();
+
+  // These parameters configure the initial probes. First we send one or two
+  // probes of sizes p1 * start_bitrate_bps_ and p2 * start_bitrate_bps_.
+  // Then whenever we get a bitrate estimate of at least further_probe_threshold
+  // times the size of the last sent probe we'll send another one of size
+  // step_size times the new estimate.
+  FieldTrialParameter<double> first_exponential_probe_scale_;
+  FieldTrialOptional<double> second_exponential_probe_scale_;
+  FieldTrialParameter<double> further_exponential_probe_scale_;
+  FieldTrialParameter<double> further_probe_threshold;
+
+  // Configures how often we send ALR probes and how big they are.
+  FieldTrialParameter<TimeDelta> alr_probing_interval_;
+  FieldTrialParameter<double> alr_probe_scale_;
+};
+
 // This class controls initiation of probing to estimate initial channel
 // capacity. There is also support for probing during a session when max
 // bitrate is adjusted by an application.
@@ -63,9 +85,6 @@
   RTC_WARN_UNUSED_RESULT std::vector<ProbeClusterConfig> RequestProbe(
       int64_t at_time_ms);
 
-  RTC_WARN_UNUSED_RESULT std::vector<ProbeClusterConfig>
-  InitiateCapacityProbing(int64_t bitrate_bps, int64_t at_time_ms);
-
   // Sets a new maximum probing bitrate, without generating a new probe cluster.
   void SetMaxBitrate(int64_t max_bitrate_bps);
 
@@ -90,7 +109,7 @@
   InitiateExponentialProbing(int64_t at_time_ms);
   RTC_WARN_UNUSED_RESULT std::vector<ProbeClusterConfig> InitiateProbing(
       int64_t now_ms,
-      std::initializer_list<int64_t> bitrates_to_probe,
+      std::vector<int64_t> bitrates_to_probe,
       bool probe_further);
 
   bool network_available_;
@@ -118,6 +137,8 @@
 
   int32_t next_probe_cluster_id_ = 1;
 
+  ProbeControllerConfig config_;
+
   RTC_DISALLOW_COPY_AND_ASSIGN(ProbeController);
 };