[ObjC ARC] Converts ios/chrome/browser/net:unit_tests to ARC.Automatically generated ARCMigrate c…

ios/chrome/browser/net/retryable_url_fetcher_unittest.mm

Index: ios/chrome/browser/net/retryable_url_fetcher_unittest.mm
diff --git a/ios/chrome/browser/net/retryable_url_fetcher_unittest.mm b/ios/chrome/browser/net/retryable_url_fetcher_unittest.mm
index 43593dc1183f55d9612fa024d6ce70269dff57c9..72c82ca621ae7e31434f998c3df6135b4fd0ea7e 100644
--- a/ios/chrome/browser/net/retryable_url_fetcher_unittest.mm
+++ b/ios/chrome/browser/net/retryable_url_fetcher_unittest.mm
@@ -13,6 +13,10 @@
 #import "testing/gtest_mac.h"
 #include "testing/platform_test.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 // An arbitrary text string for a fake response.
 NSString* const kFakeResponseString = @"Something interesting here.";