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

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

Index: ios/public/provider/chrome/browser/signin/fake_chrome_identity.mm
diff --git a/ios/public/provider/chrome/browser/signin/fake_chrome_identity.mm b/ios/public/provider/chrome/browser/signin/fake_chrome_identity.mm
index 9cf8997296e40e5eff3251f5654b54ef64112e71..1773adedf3526a94460ba09e8d4919585f6f0823 100644
--- a/ios/public/provider/chrome/browser/signin/fake_chrome_identity.mm
+++ b/ios/public/provider/chrome/browser/signin/fake_chrome_identity.mm
@@ -4,13 +4,12 @@
 
 #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
@@ -26,11 +25,10 @@
                          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;
 }