Cannot close tabs or change tab focus

[alexwykoff]

Did you search for similar issues before submitting this one?
Yes

Describe the issue you encountered:
While testing 0.12.9 Preview 1, I opened many tabs in window 1. I left it in the background for a considerable time. I would occasionally use one or two tabs in window 1. I later opened window 2 and watched a clip of a movie on Netflix. After closing that window, I returned to window 1 and found that I could not close the tab or change tabs. I then opened the developer console and found numerous errors.

Expected behavior:
Tabs should be able to close or change focus.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  Tested on OS X

• Brave Version:
  0.12.9 Preview 1

• Steps to reproduce:

  1. Please see above. It will likely be sporadic/heizenbuggy so I have saved off my data in an archive I will share with the internal team.

• Screenshot if needed:
  

• Any related issues:

[bbondy]

I think this is the same as #5560
So I'll close as a dupe, but keep in the milestone to make sure it goes through testing.