Middle mouse click doesn't close tabs

[ayumi]

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

• Describe the issue you encountered:
  Middle mouse button doesn't close tabs anymore.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  MacOS

• Brave Version (revision SHA):
  0.13.3pre2 release / b8d7358

• Steps to reproduce:

  1. Open a new tab
  2. Middle mouse click the tab
  3. see what happens

• Actual result:
  Nothing

• Expected result:
  Tab should close

• Will the steps above reproduce in a fresh profile? If not what other info can be added?
  Yes

• Is this an issue in the currently released version?
  No, prerelease