Make possible to activate adaptive AGC2 in the APM.

We update the configuration settings for AGC2. We also update their
effects. Now, 'gain_controller2.enable=true' means 'first run Adaptive
AGC2; then run AGC2 limiter'.

Previously, only the AGC2 limiter was implemented. To run that, one
had to set both 'gain_controller2.enable=true' and
'gain_controller2.enable_limiter=true'.

This setting also enables adaptive AGC2 in the test tool 'audioproc_f'.

Bug: webrtc:7494
Change-Id: I0d5dfe443f2cdc0ecf3aa4054442dab6276d284d
Reviewed-on: https://webrtc-review.googlesource.com/64990
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Alex Loiko <aleloi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22669}
diff --git a/modules/audio_processing/gain_controller2.h b/modules/audio_processing/gain_controller2.h
index 6de4564..e2ca05e 100644
--- a/modules/audio_processing/gain_controller2.h
+++ b/modules/audio_processing/gain_controller2.h
@@ -14,6 +14,7 @@
 #include <memory>
 #include <string>
 
+#include "modules/audio_processing/agc2/adaptive_agc.h"
 #include "modules/audio_processing/agc2/fixed_gain_controller.h"
 #include "modules/audio_processing/include/audio_processing.h"
 #include "rtc_base/constructormagic.h"
@@ -41,8 +42,9 @@
  private:
   static int instance_count_;
   std::unique_ptr<ApmDataDumper> data_dumper_;
-  FixedGainController gain_controller_;
+  FixedGainController fixed_gain_controller_;
   AudioProcessing::Config::GainController2 config_;
+  AdaptiveAgc adaptive_agc_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(GainController2);
 };