Replace field trials with WebRtcKeyValueConfig in PacedSender

Replaces use of field trials in PacedSender with injectable WebRtcKeyValueConfig.
Implementation still defaults to field trials.

BUG: webrtc:10335
Change-Id: Ie8870d93d51e996e762f2c2de7545bad261b6bb7
Reviewed-on: https://webrtc-review.googlesource.com/c/123521
Commit-Queue: Per Kjellander <perkj@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26818}

modules/pacing/BUILD.gn

@@ -29,7 +29,9 @@ rtc_static_library("pacing") {
   deps = [
     ":interval_budget",
     "..:module_api",
+    "../../api/transport:field_trial_based_config",
     "../../api/transport:network_control",
+    "../../api/transport:webrtc_key_value_config",
     "../../logging:rtc_event_bwe",
     "../../logging:rtc_event_log_api",
     "../../logging:rtc_event_pacing",

modules/pacing/DEPS

@@ -1,4 +1,6 @@
 include_rules = [
-  "+system_wrappers",
+  "+system_wrappers", 
+  # Avoid directly using field_trial. Instead use WebRtcKeyValueConfig.
+  "-system_wrappers/include/field_trial.h",  
   "+logging/rtc_event_log"
 ]

modules/pacing/paced_sender.cc

@@ -22,8 +22,8 @@
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 #include "system_wrappers/include/clock.h"
-#include "system_wrappers/include/field_trial.h"
 
+namespace webrtc {
 namespace {
 // Time limit in milliseconds between packet bursts.
 const int64_t kDefaultMinPacketLimitMs = 5;
@@ -35,23 +35,44 @@ const int64_t kMaxElapsedTimeMs = 2000;
 // time.
 const int64_t kMaxIntervalTimeMs = 30;
 
-}  // namespace
+bool IsDisabled(const WebRtcKeyValueConfig& field_trials,
+                absl::string_view key) {
+  return field_trials.Lookup(key).find("Disabled") == 0;
+}
 
-namespace webrtc {
+bool IsEnabled(const WebRtcKeyValueConfig& field_trials,
+               absl::string_view key) {
+  return field_trials.Lookup(key).find("Enabled") == 0;
+}
+
+}  // namespace
 
 const int64_t PacedSender::kMaxQueueLengthMs = 2000;
 const float PacedSender::kDefaultPaceMultiplier = 2.5f;
 
 PacedSender::PacedSender(Clock* clock,
                          PacketSender* packet_sender,
-                         RtcEventLog* event_log)
+                         RtcEventLog* event_log,
+                         const WebRtcKeyValueConfig* field_trials)
+    : PacedSender(clock,
+                  packet_sender,
+                  event_log,
+                  field_trials
+                      ? *field_trials
+                      : static_cast<const webrtc::WebRtcKeyValueConfig&>(
+                            FieldTrialBasedConfig())) {}
+
+PacedSender::PacedSender(Clock* clock,
+                         PacketSender* packet_sender,
+                         RtcEventLog* event_log,
+                         const WebRtcKeyValueConfig& field_trials)
     : clock_(clock),
       packet_sender_(packet_sender),
       alr_detector_(),
-      drain_large_queues_(!field_trial::IsDisabled("WebRTC-Pacer-DrainQueue")),
+      drain_large_queues_(!IsDisabled(field_trials, "WebRTC-Pacer-DrainQueue")),
       send_padding_if_silent_(
-          field_trial::IsEnabled("WebRTC-Pacer-PadInSilence")),
-      pace_audio_(!field_trial::IsDisabled("WebRTC-Pacer-BlockAudio")),
+          IsEnabled(field_trials, "WebRTC-Pacer-PadInSilence")),
+      pace_audio_(!IsDisabled(field_trials, "WebRTC-Pacer-BlockAudio")),
       min_packet_limit_ms_("", kDefaultMinPacketLimitMs),
       last_timestamp_ms_(clock_->TimeInMilliseconds()),
       paused_(false),
@@ -76,7 +97,7 @@ PacedSender::PacedSender(Clock* clock,
                            "pushback experiment must be enabled.";
   }
   ParseFieldTrial({&min_packet_limit_ms_},
-                  field_trial::FindFullName("WebRTC-Pacer-MinPacketLimitMs"));
+                  field_trials.Lookup("WebRTC-Pacer-MinPacketLimitMs"));
   UpdateBudgetWithElapsedTime(min_packet_limit_ms_);
 }
 

modules/pacing/paced_sender.h

@@ -17,7 +17,9 @@
 #include <memory>
 
 #include "absl/types/optional.h"
+#include "api/transport/field_trial_based_config.h"
 #include "api/transport/network_types.h"
+#include "api/transport/webrtc_key_value_config.h"
 #include "modules/pacing/bitrate_prober.h"
 #include "modules/pacing/interval_budget.h"
 #include "modules/pacing/pacer.h"
@@ -71,7 +73,8 @@ class PacedSender : public Pacer {
 
   PacedSender(Clock* clock,
               PacketSender* packet_sender,
-              RtcEventLog* event_log);
+              RtcEventLog* event_log,
+              const WebRtcKeyValueConfig* field_trials = nullptr);
 
   ~PacedSender() override;
 
@@ -147,6 +150,11 @@ class PacedSender : public Pacer {
   void SetQueueTimeLimit(int limit_ms);
 
  private:
+  PacedSender(Clock* clock,
+              PacketSender* packet_sender,
+              RtcEventLog* event_log,
+              const WebRtcKeyValueConfig& field_trials);
+
   int64_t UpdateTimeAndGetElapsedMs(int64_t now_us)
       RTC_EXCLUSIVE_LOCKS_REQUIRED(critsect_);
   bool ShouldSendKeepalive(int64_t at_time_us) const