[ObjC ARC] Converts ios/chrome/browser:browser to ARC.

ios/chrome/browser/app_startup_parameters.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef IOS_CHROME_BROWSER_APP_STARTUP_PARAMETERS_H_
 #define IOS_CHROME_BROWSER_APP_STARTUP_PARAMETERS_H_
 
 #import <Foundation/Foundation.h>
 
 class GURL;
 @class XCallbackParameters;
 
 // This class stores all the parameters relevant to the app startup in case
 // of launch from another app.
 @interface AppStartupParameters : NSObject
 
 // The URL received that should be opened.
 @property(nonatomic, readonly, assign) const GURL& externalURL;
 
 // Parameters representing an x-callback-url request from another app.
 // Can be nil.
-@property(nonatomic, readonly, retain) XCallbackParameters* xCallbackParameters;
+@property(nonatomic, readonly, strong) XCallbackParameters* xCallbackParameters;
 
 // Boolean to track if a voice search is requested at startup.
 @property(nonatomic, readwrite, assign) BOOL launchVoiceSearch;
 // Boolean to track if the app should launch in incognito mode.
 @property(nonatomic, readwrite, assign) BOOL launchInIncognito;
 // Boolean to track if a QR scanner is requested at startup.
 @property(nonatomic, readwrite, assign) BOOL launchQRScanner;
 
 - (instancetype)init NS_UNAVAILABLE;
 
 - (instancetype)initWithExternalURL:(const GURL&)externalURL;
 
 - (instancetype)initWithExternalURL:(const GURL&)externalURL
                 xCallbackParameters:(XCallbackParameters*)xCallbackParameters
     NS_DESIGNATED_INITIALIZER;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_APP_STARTUP_PARAMETERS_H_