Adding activation logic of the new APM level control functionality using MediaConstraints

webrtc/media/engine/webrtcvoiceengine.cc

Index: webrtc/media/engine/webrtcvoiceengine.cc
diff --git a/webrtc/media/engine/webrtcvoiceengine.cc b/webrtc/media/engine/webrtcvoiceengine.cc
index 2ddf67dd3a6d76d70236b8562cf2d5d8208bbd70..9ebd0f1888a3cbfa562de24529063698974973f6 100644
--- a/webrtc/media/engine/webrtcvoiceengine.cc
+++ b/webrtc/media/engine/webrtcvoiceengine.cc
@@ -560,6 +560,7 @@ WebRtcVoiceEngine::WebRtcVoiceEngine(
     options.delay_agnostic_aec = rtc::Optional<bool>(false);
     options.experimental_ns = rtc::Optional<bool>(false);
     options.intelligibility_enhancer = rtc::Optional<bool>(false);
+    options.level_control = rtc::Optional<bool>(false);
     bool error = ApplyOptions(options);
     RTC_DCHECK(error);
   }
@@ -683,9 +684,27 @@ bool WebRtcVoiceEngine::ApplyOptions(const AudioOptions& options_in) {
     }
   }
 
+  // Use optional to avoid uneccessary calls to BuiltInAGCIsAvailable while
+  // complying with the unittest requirements of only 1 call per test.
+  rtc::Optional<bool> built_in_agc_avaliable;
+  if (options.level_control) {
+    if (!built_in_agc_avaliable) {
+      built_in_agc_avaliable =
+          rtc::Optional<bool>(adm()->BuiltInAGCIsAvailable());
+    }
+    if (*built_in_agc_avaliable) {
+      // Disable internal software level control if built-in AGC is enabled,
+      // i.e., replace the software AGC with the built-in AGC.
+      options.level_control = rtc::Optional<bool>(false);
+    }
+  }
+
   if (options.auto_gain_control) {
-    const bool built_in_agc = adm()->BuiltInAGCIsAvailable();
-    if (built_in_agc) {
+    if (!built_in_agc_avaliable) {
+      built_in_agc_avaliable =
+          rtc::Optional<bool>(adm()->BuiltInAGCIsAvailable());
+    }
+    if (*built_in_agc_avaliable) {
       if (adm()->EnableBuiltInAGC(*options.auto_gain_control) == 0 &&
           *options.auto_gain_control) {
         // Disable internal software AGC if built-in AGC is enabled,
@@ -842,6 +861,18 @@ bool WebRtcVoiceEngine::ApplyOptions(const AudioOptions& options_in) {
         new webrtc::Intelligibility(*intelligibility_enhancer_));
   }
 
+  if (options.level_control) {
+    level_control_ = options.level_control;
+  }
+
+  if (level_control_) {
+    LOG(LS_INFO) << "Level Control is " << (*level_control_ ? "" : "not ")
+                 << "enabled";

[tommi, 2016/06/27 08:34:33]

My preference is to keep the amount of code for informational logging, down. 
The code behind the two log statements dwarves the actual functionality.  I'd go
with one LOG line, and keep the code size down:

LOG((LS_INFO) << "Level control: " << level_control_ ? *level_control_ : -1;
if (level_control_) {
  config.Set<webrtc::LevelControl>(new webrtc::LevelControl(*level_control_));
}

[peah-webrtc, 2016/06/27 08:41:12]

That looks great! 

Done.

+    config.Set<webrtc::LevelControl>(new webrtc::LevelControl(*level_control_));
+  } else {
+    LOG(LS_INFO) << "Level Control is not enabled.";
+  }
+
   // We check audioproc for the benefit of tests, since FakeWebRtcVoiceEngine
   // returns NULL on audio_processing().
   webrtc::AudioProcessing* audioproc = voe_wrapper_->base()->audio_processing();