>… so doesn't have access to it many requests the browser will make outside of that scope.

You have access if you chose to modify/recompile the .cpp/.rs files that deal with sending requests that those higher level functions use, this is what I do.

Some particular places of interest on /mozilla-central/:

- /servo/components/style/gecko/urls.rs, will pertain to calls called from css image functions

- /netwerk/protocol/http/nsHttpHandler.cpp, some classess that deal with handling things related to sending all http requests