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

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 1d8e043cce410adbb1b07e970b41bf75f08a4395..453b7c78f1419837f2df83c6e034dedacc8fa294 100644
--- a/webrtc/modules/audio_processing/level_controller/level_controller.h
+++ b/webrtc/modules/audio_processing/level_controller/level_controller.h
@@ -15,6 +15,7 @@
 #include <vector>
 
 #include "webrtc/base/constructormagic.h"
+#include "webrtc/base/gtest_prod_util.h"
 #include "webrtc/base/optional.h"
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
 #include "webrtc/modules/audio_processing/level_controller/gain_applier.h"
@@ -38,6 +39,10 @@ class LevelController {
   void Process(AudioBuffer* audio);
   float GetLastGain() { return last_gain_; }
 
+  // TODO(peah): This method is a temporary solution as the the aim is to
+  // instead apply the config inside the constructor. Therefore this is likely
+  // to change.
+  void ApplyConfig(const AudioProcessing::Config::LevelController& config);
   // Validates a config.
   static bool Validate(const AudioProcessing::Config::LevelController& config);
   // Dumps a config to a string.
@@ -45,6 +50,7 @@ class LevelController {
       const AudioProcessing::Config::LevelController& config);
 
  private:
+  FRIEND_TEST_ALL_PREFIXES(LevelControllerConfig, InitialLevel);

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

You should try to make do without declaring all tests as friends. This pattern
makes sense for the APM, since the APM interface is harder to change and the
impl is very large at the moment, but this is fairly new code, and internal, so
it can be changed to make testing easier.

If absolutely necessary, add a "NnnForTesting()" utility function. Exposing ALL
the internals of the class to tests blurs the expectations of the test and class
interface.

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

I fully agree  with you your comment about FRIEND classes. 

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.

   class Metrics {
    public:
     Metrics() { Initialize(AudioProcessing::kSampleRate48kHz); }
@@ -80,6 +86,8 @@ class LevelController {
   float dc_level_[2];
   float dc_forgetting_factor_;
   float last_gain_;
+  bool gain_jumpstart_ = false;
+  AudioProcessing::Config::LevelController config_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(LevelController);
 };