Add RetainedRef uses where needed.

chrome/browser/sync_file_system/local/root_delete_helper.cc

Index: chrome/browser/sync_file_system/local/root_delete_helper.cc
diff --git a/chrome/browser/sync_file_system/local/root_delete_helper.cc b/chrome/browser/sync_file_system/local/root_delete_helper.cc
index 63a90008b862a5e082a7edde3cea69a640842afc..ff36cefe9ba9e3d3d5ba4f2759d22b195c4fee77 100644
--- a/chrome/browser/sync_file_system/local/root_delete_helper.cc
+++ b/chrome/browser/sync_file_system/local/root_delete_helper.cc
@@ -76,8 +76,8 @@ void RootDeleteHelper::DidDeleteFileSystem(base::File::Error error) {
   // TODO(kinuko): This should be probably automatically handled in
   // DeleteFileSystem via QuotaUtil::DeleteOriginDataOnFileThread.
   file_system_context_->default_file_task_runner()->PostTaskAndReply(
-      FROM_HERE,
-      base::Bind(&ResetFileChangeTracker, file_system_context_, url_),
+      FROM_HERE, base::Bind(&ResetFileChangeTracker,
+                            base::RetainedRef(file_system_context_), url_),
       base::Bind(&RootDeleteHelper::DidResetFileChangeTracker,
                  weak_factory_.GetWeakPtr()));
 }