Just a quick update to my chrome extension tonight. I recently had an email asking if there was a way I could make it so that you could send a Tweet at the same time as posting to Tumblr.
After a quick check on the Tumblr API to confirm that yes Tumblr supports the "post-to-twitter" option I spun out this little option.
So now you have three options for tweeting when posting: "no", "auto" and "prompt".
Chrome should auto-update the extension for you soon. If you dont have it hope over to the gallery page here.