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

ios/public/provider/chrome/browser/signin/fake_chrome_identity.mm

 // Copyright 2016 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/public/provider/chrome/browser/signin/fake_chrome_identity.h"
 
-#import "base/mac/scoped_nsobject.h"
 
 @implementation FakeChromeIdentity {
-  base::scoped_nsobject<NSString> _userEmail;
-  base::scoped_nsobject<NSString> _gaiaID;
-  base::scoped_nsobject<NSString> _userFullName;
-  base::scoped_nsobject<NSString> _hashedGaiaID;
+  NSString* _userEmail;
+  NSString* _gaiaID;
+  NSString* _userFullName;
+  NSString* _hashedGaiaID;
 }
 
 + (FakeChromeIdentity*)identityWithEmail:(NSString*)email
                                   gaiaID:(NSString*)gaiaID
                                     name:(NSString*)name {
   return
       [[[FakeChromeIdentity alloc] initWithEmail:email gaiaID:gaiaID name:name]
           autorelease];
 }
 
 - (instancetype)initWithEmail:(NSString*)email
                        gaiaID:(NSString*)gaiaID
                          name:(NSString*)name {
   self = [super init];
   if (self) {
-    _userEmail.reset([email copy]);
-    _gaiaID.reset([gaiaID copy]);
-    _userFullName.reset([name copy]);
-    _hashedGaiaID.reset(
-        [[NSString stringWithFormat:@"%@_hashID", name] retain]);
+    _userEmail = [email copy];
+    _gaiaID = [gaiaID copy];
+    _userFullName = [name copy];
+    _hashedGaiaID = [[NSString stringWithFormat:@"%@_hashID", name] retain];
   }
   return self;
 }
 
 - (NSString*)userEmail {
   return _userEmail;
 }
 
 - (NSString*)gaiaID {
   return _gaiaID;
 }
 
 - (NSString*)userFullName {
   return _userFullName;
 }
 
 - (NSString*)hashedGaiaID {
   return _hashedGaiaID;
 }
 
 @end