You are doing the right thing! The 204 "No Content" response is expected, it simply means that the New Relic server received your message and didn't have any information to send back to you.
request_name
is whatever you want it to be. You probably want it to be a name specific to this element. It will show up as a new item in the "Page views" dashboard of the Browser section in the New Relic APM website. Note, however, that it shouldn't be a dynamic name, such as a user name or email address. Instead it should describe the item you are timing. You might use "username" or "email address" instead of the actual user name or email address of the logged in user.It will show up in the "Page views" dashboard of the Browser section of the New Relic APM website.
We have not introduced any new features for tracking timing outside of AJAX requests.