To test, open the Inspector on this page, go to the Resources panel.
First off, you should be able to actually select each "abc" resource to see the HTTP info / content. Bug 30079 didn't allow you to select all of these.
For each of the "abc" resources open the HTTP Information and Request Payload tree elements above the content. One of the resources will not have a Request Payload.
There should be one each of the following resources:
One with a Request Method: GET and no Request Payload
One with a Request Method: POST and Request Payload of "123"
One with a Request Method: POST and Request Payload of "456"
Another change made by this bug was to change the way the drag/drop of the resource itself worked. The previous method of handling drag/drop of the resource was actually causing the unselectability. So the drag/drop of the resources needs to be tested as well.
Select one of the resources.
Drag it to an application that can accept text or a link
The application should provide some feedback indicating it will accept the drop, but may not