APM: remove unused field trial in `AgcManagerDirect`

The removed field trial was added in
https://webrtc-review.googlesource.com/c/src/+/160708.

Bug: webrtc:7494
Change-Id: I1abe51ea086342666a0420d5c10ddea87810aa26
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/278781
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38366}
diff --git a/modules/audio_processing/agc/agc_manager_direct.cc b/modules/audio_processing/agc/agc_manager_direct.cc
index d8746b6..4114eaa 100644
--- a/modules/audio_processing/agc/agc_manager_direct.cc
+++ b/modules/audio_processing/agc/agc_manager_direct.cc
@@ -63,12 +63,6 @@
 using AnalogAgcConfig =
     AudioProcessing::Config::GainController1::AnalogGainController;
 
-// Returns whether a fall-back solution to choose the maximum level should be
-// chosen.
-bool UseMaxAnalogChannelLevel() {
-  return field_trial::IsEnabled("WebRTC-UseMaxAnalogAgcChannelLevel");
-}
-
 // If the "WebRTC-Audio-2ndAgcMinMicLevelExperiment" field trial is specified,
 // parses it and returns a value between 0 and 255 depending on the field-trial
 // string. Returns an unspecified value if the field trial is not specified, if
@@ -486,7 +480,6 @@
     : analog_controller_enabled_(analog_config.enabled),
       min_mic_level_override_(GetMinMicLevelOverride()),
       data_dumper_(new ApmDataDumper(instance_counter_.fetch_add(1) + 1)),
-      use_min_channel_level_(!UseMaxAnalogChannelLevel()),
       num_capture_channels_(num_capture_channels),
       disable_digital_adaptive_(!analog_config.enable_digital_adaptive),
       frames_since_clipped_(analog_config.clipped_wait_frames),
@@ -714,21 +707,11 @@
   int new_recommended_input_volume =
       channel_agcs_[0]->recommended_analog_level();
   channel_controlling_gain_ = 0;
-  if (use_min_channel_level_) {
-    for (size_t ch = 1; ch < channel_agcs_.size(); ++ch) {
-      int level = channel_agcs_[ch]->recommended_analog_level();
-      if (level < new_recommended_input_volume) {
-        new_recommended_input_volume = level;
-        channel_controlling_gain_ = static_cast<int>(ch);
-      }
-    }
-  } else {
-    for (size_t ch = 1; ch < channel_agcs_.size(); ++ch) {
-      int level = channel_agcs_[ch]->recommended_analog_level();
-      if (level > new_recommended_input_volume) {
-        new_recommended_input_volume = level;
-        channel_controlling_gain_ = static_cast<int>(ch);
-      }
+  for (size_t ch = 1; ch < channel_agcs_.size(); ++ch) {
+    int level = channel_agcs_[ch]->recommended_analog_level();
+    if (level < new_recommended_input_volume) {
+      new_recommended_input_volume = level;
+      channel_controlling_gain_ = static_cast<int>(ch);
     }
   }
 
diff --git a/modules/audio_processing/agc/agc_manager_direct.h b/modules/audio_processing/agc/agc_manager_direct.h
index e9cf0b9..53d63ad 100644
--- a/modules/audio_processing/agc/agc_manager_direct.h
+++ b/modules/audio_processing/agc/agc_manager_direct.h
@@ -153,7 +153,6 @@
   const absl::optional<int> min_mic_level_override_;
   std::unique_ptr<ApmDataDumper> data_dumper_;
   static std::atomic<int> instance_counter_;
-  const bool use_min_channel_level_;
   const int num_capture_channels_;
   const bool disable_digital_adaptive_;