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/base/gtest_prod_util.h"
+#include "webrtc/modules/audio_processing/level_controller/lc_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:
+  FRIEND_TEST_ALL_PREFIXES(LevelControllerConfig, InitialLevel);

[the sun, 2016/09/30 08:51:16]

Try to get by without these, please. In particular exposing the internals to the
LevelControllerConfig test seems dubious. If they're so tightly coupled, why
have separate classes in the first place?

Adding a unit test for the peak follower is more appropriate (and then you could
test the handling of the initial peak level implicitly).

[peah-webrtc, 2016/10/03 09:52:14]

I don't think this is really related to the coupling of classes but rather to
how to test that the specified parameters stick. 

I fully agree  with you your comment about FRIEND classes. 
After offline discussions we decided to not explicitly verify that the specified
settings take effect, and instead leave that to the bitexactness tests.
I have changed the code accordingly. PTAL.

[the sun, 2016/10/06 07:21:13]

Acknowledged.

   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_