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

ios/chrome/browser/app_startup_parameters.mm

 // 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.
 
 #import "ios/chrome/browser/app_startup_parameters.h"
 
 #include "base/logging.h"
-#import "base/mac/scoped_nsobject.h"
 #include "ios/chrome/browser/experimental_flags.h"
 #import "ios/chrome/browser/xcallback_parameters.h"
 #include "url/gurl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @implementation AppStartupParameters {
   GURL _externalURL;
-  base::scoped_nsobject<XCallbackParameters> _xCallbackParameters;
   BOOL _launchVoiceSearch;
   BOOL _launchInIncognito;
   BOOL _launchQRScanner;
 }
 
 @synthesize launchVoiceSearch = _launchVoiceSearch;
 @synthesize launchInIncognito = _launchInIncognito;
+@synthesize xCallbackParameters = _xCallbackParameters;
 
 - (const GURL&)externalURL {
   return _externalURL;
 }
 
-- (XCallbackParameters*)xCallbackParameters {
-  return _xCallbackParameters.get();
-}
 
 - (instancetype)init {
   NOTREACHED();
   return nil;
 }
 
 - (instancetype)initWithExternalURL:(const GURL&)externalURL {
   return [self initWithExternalURL:externalURL xCallbackParameters:nil];
 }
 
 - (instancetype)initWithExternalURL:(const GURL&)externalURL
                 xCallbackParameters:(XCallbackParameters*)xCallbackParameters {
   self = [super init];
   if (self) {
-    _externalURL = GURL(externalURL);
-    _xCallbackParameters.reset([xCallbackParameters retain]);
+    _externalURL = externalURL;
+    _xCallbackParameters = xCallbackParameters;
   }
   return self;
 }
 
 - (NSString*)description {
   return [NSString stringWithFormat:@"ExternalURL: %s \nXCallbackParams: %@",
                                     _externalURL.spec().c_str(),
-                                    _xCallbackParameters.get()];
+                                    _xCallbackParameters];
 }
 
 #pragma mark Property implementation.
 
 - (BOOL)launchQRScanner {
   return _launchQRScanner && experimental_flags::IsQRCodeReaderEnabled();
 }
 
 - (void)setLaunchQRScanner:(BOOL)launch {
   _launchQRScanner = launch;
 }
 
 @end