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.h b/sdk/objc/base/RTCLogging.h
index be62db2..754945c 100644
--- a/sdk/objc/base/RTCLogging.h
+++ b/sdk/objc/base/RTCLogging.h
@@ -18,6 +18,7 @@
   RTCLoggingSeverityInfo,
   RTCLoggingSeverityWarning,
   RTCLoggingSeverityError,
+  RTCLoggingSeverityNone,
 };
 
 // Wrapper for C++ RTC_LOG(sev) macros.