Reproducing the Firefox memory leak glitch

I first spotted this bug with version 35 and it's still present, though only slightly improved, with version 39.0.3. I'm running it under Windows 7 Pro SP1, fully updated as of August 7, 2015. This bug is present in Firefox's safe mode which means it's not caused by plug-ins, add-ons, themes, etc. The issue is with Firefox itself. I have a 100% success rate on reproducing this bug as well. This video shows how I reproduce the bug:

1. Start Firefox in safe mode. Hold shift while clicking on the icon to start it up then click the appropriate button.
2. Go to Facebook and, if needed, log in.
3. Go to your profile and look at your friends list. For best results, I would recommend at least 500 friends.
4. Scroll all the way down so that everyone in the friends list loads and the next section shows up.
5. Right-click on someone's profile name and choose "open in new window".
6. Scroll down a bit to get new content to load. About 4 to 10 extensions for more content is good enough.
7. Close the new window.
8. Repeat steps 5 to 7 several dozen times, choosing new names each time.
9. After a short bit, you'll find that Firefox hangs and the memory usage shoots up from 500 MB to start to over 1 GB with increasing CPU usage.
10. After a while, Firefox starts throwing up a "not responding" notice, usually by the time you get to about 1.5 GB memory usage.
11. Continue on until Firefox gets to about 3.5 GB of memory usage. Do an "about:memory" before that and note the results - detached windows dominate.
12. Once you push past 3.5 GB, Firefox completely stops responding altogether and may crash.

Just 2 windows actually open, starting with 250 MB memory usage, and it turns into 3.5 GB with the same 2 windows.

This video has the contents on Facebook blurred for privacy reasons - note how the memory usage in Windows Task Manager climbs a lot but kind of resets a bit. With version 35, the resetting didn't happen. However, it eventually got to the point where Firefox just all out crashes and I have a crash report. I also had to scale it down from 1920x1440 to fit in the 1920x1080 full HD size. In addition, because this takes so long, I'm having it play back at double the true speed. There is no audio.

Actual bug report: https://bugzilla.mozilla.org/show_bug.cgi?id=1116992