Adding support for logging severity LS_NONE.

Bug: webrtc:8735
Change-Id: I07247ce67983f873febb8d8d32c25032a4608eae
Reviewed-on: https://webrtc-review.googlesource.com/c/40400
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Commit-Queue: Peter Hanspers <peterhanspers@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25197}
diff --git a/sdk/objc/base/RTCLogging.mm b/sdk/objc/base/RTCLogging.mm
index 5c8f9fb..e8dae02 100644
--- a/sdk/objc/base/RTCLogging.mm
+++ b/sdk/objc/base/RTCLogging.mm
@@ -22,6 +22,8 @@
       return rtc::LS_WARNING;
     case RTCLoggingSeverityError:
       return rtc::LS_ERROR;
+    case RTCLoggingSeverityNone:
+      return rtc::LS_NONE;
   }
 }