I don't know much about how Google Chrome or SQLite works, but I know that Chrome makes heavy use of threads (I think a thread per tab). Additionally, I know that SQLite suggests to use a client-server database if parallel access is required. I'm not sure, but I assume Chrome uses SQLite like Firefox does, to save cookies.
Therefore, I think it's quite likely that parallel access to the database happens (because every Tab needs the ability to save cookies).
Therefore, it doesn't make sense to me why Google Chrome uses SQLite.