Right click new tab icon (+) also processes left click event

[bsclifton]

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

• Describe the issue you encountered:
  Right clicking the new tab button (the + icon next to the row of tabs) is supposed to present a menu with: new tab / new session tab / new private tab / new window

The right / middle click behaviors were changed with Chromium 56 and I believe this behavior had an unintentional regression with 40d9979

The menu does show, but it also sends a click.

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

• Brave Version (revision SHA):
  0.13.4

• Steps to reproduce:

  1. Launch Brave
  2. Right click on new tab icon (+)

• Actual result:
  Menu is shown AND a new tab is opened

• Expected result:
  Only menu is shown

• 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?
  yes

• Can this issue be consistently reproduced?
  yes

[cndouglas]

Also happens with right-clicking the refresh button.