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

ios/chrome/browser/file_metadata_util.mm

Index: ios/chrome/browser/file_metadata_util.mm
diff --git a/ios/chrome/browser/file_metadata_util.mm b/ios/chrome/browser/file_metadata_util.mm
index cad6d449ccef8dd94399ab68fb0726686e2fe3f9..dbbb174af8ac821a95391720f7f4caf623878452 100644
--- a/ios/chrome/browser/file_metadata_util.mm
+++ b/ios/chrome/browser/file_metadata_util.mm
@@ -10,6 +10,10 @@
 #include "base/strings/sys_string_conversions.h"
 #include "base/threading/thread_restrictions.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 void SetSkipSystemBackupAttributeToItem(const base::FilePath& path,
                                         bool skip_system_backup) {
   base::ThreadRestrictions::AssertIOAllowed();