Added a level controller initialization value to 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 9636ff32fc4fc98a21402e6d11c4d1433da6ed10..454fae45b4616c2659eb7a76037d9c0b01047a4d 100644
--- a/webrtc/media/engine/webrtcvoiceengine.cc
+++ b/webrtc/media/engine/webrtcvoiceengine.cc
@@ -872,6 +872,10 @@ bool WebRtcVoiceEngine::ApplyOptions(const AudioOptions& options_in) {
   webrtc::AudioProcessing::Config apm_config;
   if (level_control_) {
     apm_config.level_controller.enabled = *level_control_;
+    if (options.level_control_initial_peak_level_dbfs) {
+      apm_config.level_controller.initial_peak_level_dbfs =
+          *options.level_control_initial_peak_level_dbfs;
+    }
   }
 
   // We check audioproc for the benefit of tests, since FakeWebRtcVoiceEngine