Added a level controller initialization value to MediaConstraints.

webrtc/api/localaudiosource.cc

Index: webrtc/api/localaudiosource.cc
diff --git a/webrtc/api/localaudiosource.cc b/webrtc/api/localaudiosource.cc
index 53c426e01119900d5eeb5fd4a5524f2f619e954a..d91394eebcfca022e1e4b1270dc15985de4ab065 100644
--- a/webrtc/api/localaudiosource.cc
+++ b/webrtc/api/localaudiosource.cc
@@ -66,6 +66,18 @@ void FromConstraints(const MediaConstraintsInterface::Constraints& constraints,
         entry.value = rtc::Optional<bool>(value);
     }
   }
+
+  // Set non-boolean constraints.
+  std::string value;
+  if (constraints.FindFirst(
+          MediaConstraintsInterface::kLevelControlInitialPeakLevelDBFS,
+          &value)) {
+    float level_control_initial_peak_level_dbfs;
+    if (rtc::FromString(value, &level_control_initial_peak_level_dbfs)) {
+      options->level_control_initial_peak_level_dbfs =
+          rtc::Optional<float>(level_control_initial_peak_level_dbfs);
+    }
+  }
 }
 
 }  // namespace