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

ios/chrome/browser/autofill/form_input_egtest.mm

Index: ios/chrome/browser/autofill/form_input_egtest.mm
diff --git a/ios/chrome/browser/autofill/form_input_egtest.mm b/ios/chrome/browser/autofill/form_input_egtest.mm
index a04c5a0b3ba4ea86e76b5a57d099dbcae20f1d1f..ebebfa9c56bd0f98e001d6e2c1fae8ca37b29bf5 100644
--- a/ios/chrome/browser/autofill/form_input_egtest.mm
+++ b/ios/chrome/browser/autofill/form_input_egtest.mm
@@ -20,6 +20,10 @@
 #import "ios/web/public/test/http_server.h"
 #include "ios/web/public/test/http_server_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 
 const char kFormElementId1[] = "username";
@@ -31,7 +35,7 @@ NSString* GetFocusedElementId() {
   NSString* js = @"(function() {"
                   "  return document.activeElement.id;"
                   "})();";
-  NSError* error = nil;
+  __unsafe_unretained NSError* error = nil;
   NSString* result = chrome_test_util::ExecuteJavaScript(js, &error);
   GREYAssertTrue(!error, @"Unexpected error when executing JavaScript.");
   return result;