Called when an extension needs a browser to host a background script specified via the "background" manifest key. The browser will have no visible window and cannot be displayed. |extension| is the extension that is loading the background script. |url| is an internally generated reference to an HTML page that will be used to load the background script via a "<script>" src attribute. To allow creation of the browser optionally modify |client| and |settings| and return false (0). To cancel creation of the browser (and consequently cancel load of the background script) return true (1). Successful creation will be indicated by a call to cef_life_span_handler_t::OnAfterCreated, and