Tweaks for new Objective-C API.

webrtc/api/objc/RTCIceServer.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>
 
 NS_ASSUME_NONNULL_BEGIN
 
 @interface RTCIceServer : NSObject
 
 /** URI(s) for this server represented as NSStrings. */
-@property(nonatomic, copy, readonly) NSArray<NSString *> *urlStrings;
+@property(nonatomic, readonly) NSArray<NSString *> *urlStrings;
 
 /** Username to use if this RTCIceServer object is a TURN server. */
-@property(nonatomic, copy, readonly, nullable) NSString *username;
+@property(nonatomic, readonly, nullable) NSString *username;
 
 /** Credential to use if this RTCIceServer object is a TURN server. */
-@property(nonatomic, copy, readonly, nullable) NSString *credential;
+@property(nonatomic, readonly, nullable) NSString *credential;
 
 - (instancetype)init NS_UNAVAILABLE;
 
 /** Convenience initializer for a server with no authentication (e.g. STUN). */
 - (instancetype)initWithURLStrings:(NSArray<NSString *> *)urlStrings;
 
 /**
  * Initialize an RTCIceServer with its associated URLs, optional username,
  * optional credential, and credentialType.
  */
 - (instancetype)initWithURLStrings:(NSArray<NSString *> *)urlStrings
                           username:(nullable NSString *)username
                         credential:(nullable NSString *)credential
     NS_DESIGNATED_INITIALIZER;
 
 @end
 
 NS_ASSUME_NONNULL_END