drag-n-drop bypasses tor on Unity

Requests for drag-and-drop thumbnails in Tor Browser is not sent through the Tor network, but instead plain-text HTTP request.

How to reproduce:

• Download and start Tor Browser Bundle version 2.2.34-2 (current, this one)
• Start up Wireshark and start logging your network interactively
• Using the Tor Browser, visit "www.gnome.org" (or any other HTTP site)
• See Wireshark sending all traffic encrypted to various Tor nodes
• When the site have loaded, drag the big image on the site
• See Wireshark logging a DNS request for "www.gnome.org" with reply
• See Wireshark logging a HTTP HEAD request for "/wp-content/uploads/2011/09/gnome-3.2.png" on host "www.gnome.org", sending this directly unencrypted to the IP returned from the DNS request.