Minor ObjC header updates.

webrtc/base/objc/RTCFileLogger.h

 /*
  *  Copyright 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #import <Foundation/Foundation.h>
 
 typedef NS_ENUM(NSUInteger, RTCFileLoggerSeverity) {
-  kRTCFileLoggerSeverityVerbose,
-  kRTCFileLoggerSeverityInfo,
-  kRTCFileLoggerSeverityWarning,
-  kRTCFileLoggerSeverityError
+  RTCFileLoggerSeverityVerbose,
+  RTCFileLoggerSeverityInfo,
+  RTCFileLoggerSeverityWarning,
+  RTCFileLoggerSeverityError
 };
 
 typedef NS_ENUM(NSUInteger, RTCFileLoggerRotationType) {
-  kRTCFileLoggerTypeCall,
-  kRTCFileLoggerTypeApp,
+  RTCFileLoggerTypeCall,
+  RTCFileLoggerTypeApp,
 };
 
+NS_ASSUME_NONNULL_BEGIN
+
 // This class intercepts WebRTC logs and saves them to a file. The file size
 // will not exceed the given maximum bytesize. When the maximum bytesize is
 // reached, logs are rotated according to the rotationType specified.
 // For kRTCFileLoggerTypeCall, logs from the beginning and the end
 // are preserved while the middle section is overwritten instead.
 // For kRTCFileLoggerTypeApp, the oldest log is overwritten.
 // This class is not threadsafe.
 @interface RTCFileLogger : NSObject
 
 // The severity level to capture. The default is kRTCFileLoggerSeverityInfo.
@@ skipping 25 matching lines @@
 - (void)start;
 
 // Stops writing WebRTC logs to disk. This method is also called on dealloc.
 - (void)stop;
 
 // Returns the current contents of the logs, or nil if start has been called
 // without a stop.
 - (NSData *)logData;
 
 @end
+
+NS_ASSUME_NONNULL_END
+