Reland of added functionality for specifying the initial signal level to use for the gain estimation

webrtc/modules/audio_processing/level_controller/peak_level_estimator.h

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_MODULES_AUDIO_PROCESSING_LEVEL_CONTROLLER_PEAK_LEVEL_ESTIMATOR_H_
 #define WEBRTC_MODULES_AUDIO_PROCESSING_LEVEL_CONTROLLER_PEAK_LEVEL_ESTIMATOR_H_
 
 #include "webrtc/base/constructormagic.h"
+#include "webrtc/modules/audio_processing/level_controller/level_controller_constants.h"
 #include "webrtc/modules/audio_processing/level_controller/signal_classifier.h"
 
 namespace webrtc {
 
 class PeakLevelEstimator {
  public:
-  PeakLevelEstimator();
+  explicit PeakLevelEstimator(float initial_peak_level_dbfs);
   ~PeakLevelEstimator();
-  void Initialize();
+  void Initialize(float initial_peak_level_dbfs);
   float Analyze(SignalClassifier::SignalType signal_type,
                 float frame_peak_level);
-
  private:
   float peak_level_;
   int hold_counter_;
   bool initialization_phase_;
 
-  RTC_DISALLOW_COPY_AND_ASSIGN(PeakLevelEstimator);
+  RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(PeakLevelEstimator);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_LEVEL_CONTROLLER_PEAK_LEVEL_ESTIMATOR_H_