Introduced new scheme for controlling the functionality inside the audio processing module

webrtc/modules/audio_processing/level_controller/level_controller.h

Index: webrtc/modules/audio_processing/level_controller/level_controller.h
diff --git a/webrtc/modules/audio_processing/level_controller/level_controller.h b/webrtc/modules/audio_processing/level_controller/level_controller.h
index 65fc36005b692de46e114ca78be81f0ca1ada534..01dbf3678cb9901e91388723b38a9d80c402fe63 100644
--- a/webrtc/modules/audio_processing/level_controller/level_controller.h
+++ b/webrtc/modules/audio_processing/level_controller/level_controller.h
@@ -38,6 +38,14 @@ class LevelController {
   void Process(AudioBuffer* audio);
   float GetLastGain() { return last_gain_; }
 
+  // Validates a config.
+  static bool Validate(const AudioProcessing::Config::LevelController& config);
+  // Dumps a config to a string.
+  static std::string ToString(
+      const AudioProcessing::Config::LevelController& config);
+  // Produces a default config which is valid.
+  static AudioProcessing::Config::LevelController DefaultConfig();
+
  private:
   class Metrics {
    public: