Move AGC2 config ToString to the right place and update Validate()

The APM config to string mapping must be in one place (namely,
in `audio_processing.cc`). This CL moves the AGC2 config to string
impl to the right place.

This CL also updates `GainController2::Validate()` and adds the
missing unit tests for the parameters that have recently been added.

Stack buffer size in `AudioProcessing::Config::ToString()` increased
because of the extra params. Syntax near `multi_channel_capture` fixed.
Output string format verified with a JS linter.

Bug: webrtc:7494
Change-Id: I692e1549b7d40c970d88a14c8e83da16325fb54c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/187080
Commit-Queue: Alessio Bazzica <alessiob@webrtc.org>
Reviewed-by: Minyue Li <minyue@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32400}
diff --git a/modules/audio_processing/gain_controller2.cc b/modules/audio_processing/gain_controller2.cc
index 8e71d40..6561beb 100644
--- a/modules/audio_processing/gain_controller2.cc
+++ b/modules/audio_processing/gain_controller2.cc
@@ -65,8 +65,7 @@
 
 void GainController2::ApplyConfig(
     const AudioProcessing::Config::GainController2& config) {
-  RTC_DCHECK(Validate(config))
-      << " the invalid config was " << ToString(config);
+  RTC_DCHECK(Validate(config));
 
   config_ = config;
   if (config.fixed_digital.gain_db != config_.fixed_digital.gain_db) {
@@ -84,55 +83,19 @@
 
 bool GainController2::Validate(
     const AudioProcessing::Config::GainController2& config) {
-  return config.fixed_digital.gain_db >= 0.f &&
-         config.fixed_digital.gain_db < 50.f &&
-         config.adaptive_digital.extra_saturation_margin_db >= 0.f &&
-         config.adaptive_digital.extra_saturation_margin_db <= 100.f;
-}
-
-std::string GainController2::ToString(
-    const AudioProcessing::Config::GainController2& config) {
-  rtc::StringBuilder ss;
-  std::string adaptive_digital_level_estimator;
-  using LevelEstimatorType =
-      AudioProcessing::Config::GainController2::LevelEstimator;
-  switch (config.adaptive_digital.level_estimator) {
-    case LevelEstimatorType::kRms:
-      adaptive_digital_level_estimator = "RMS";
-      break;
-    case LevelEstimatorType::kPeak:
-      adaptive_digital_level_estimator = "peak";
-      break;
-  }
-  // clang-format off
-  // clang formatting doesn't respect custom nested style.
-  ss << "{"
-        "enabled: " << (config.enabled ? "true" : "false") << ", "
-        "fixed_digital: {gain_db: " << config.fixed_digital.gain_db << "}, "
-        "adaptive_digital: {"
-          "enabled: "
-            << (config.adaptive_digital.enabled ? "true" : "false") << ", "
-          "level_estimator: {"
-            "type: " << adaptive_digital_level_estimator << ", "
-            "adjacent_speech_frames_threshold: "
-              << config.adaptive_digital
-                  .level_estimator_adjacent_speech_frames_threshold << ", "
-            "initial_saturation_margin_db: "
-              << config.adaptive_digital.initial_saturation_margin_db << ", "
-            "extra_saturation_margin_db: "
-              << config.adaptive_digital.extra_saturation_margin_db << "}, "
-          "gain_applier: {"
-            "adjacent_speech_frames_threshold: "
-              << config.adaptive_digital
-                  .gain_applier_adjacent_speech_frames_threshold << ", "
-            "max_gain_change_db_per_second: "
-              << config.adaptive_digital.max_gain_change_db_per_second << ", "
-            "max_output_noise_level_dbfs: "
-              << config.adaptive_digital.max_output_noise_level_dbfs << "}"
-        "}"
-        "}";
-  // clang-format on
-  return ss.Release();
+  const auto& fixed = config.fixed_digital;
+  const auto& adaptive = config.adaptive_digital;
+  return fixed.gain_db >= 0.f && fixed.gain_db < 50.f &&
+         adaptive.vad_probability_attack > 0.f &&
+         adaptive.vad_probability_attack <= 1.f &&
+         adaptive.level_estimator_adjacent_speech_frames_threshold >= 1 &&
+         adaptive.initial_saturation_margin_db >= 0.f &&
+         adaptive.initial_saturation_margin_db <= 100.f &&
+         adaptive.extra_saturation_margin_db >= 0.f &&
+         adaptive.extra_saturation_margin_db <= 100.f &&
+         adaptive.gain_applier_adjacent_speech_frames_threshold >= 1 &&
+         adaptive.max_gain_change_db_per_second > 0.f &&
+         adaptive.max_output_noise_level_dbfs <= 0.f;
 }
 
 }  // namespace webrtc