This change allows the NetworkService to handle cookie load/save in cases where
cookies will not be filtered (CefResourceRequestHandler::GetCookieAccessFilter
returns null) and the request will be handled by the default network loader.
This represents a minor performance improvement by reducing the volume of cross-
process messaging in the default (no filtering or custom handing) case. Cookie
load/save still needs to be routed through the browser process if a filter is
returned, or if a CefResourceHandler is used for the request.

To test: Test expectations are unchanged.