Add OneTab Extension Support

[philkloose]

• Did you search for similar issues before submitting this one?
  Yes
• Describe the issue you encountered:
  I added the extension but the OneTab icon in the toolbar doesn't register clicks -- button is completely dead.
• Platform (Win7, 8, 10? macOS? Linux distro?):
  Win7
• Brave Version (revision SHA):

Brave: 0.14.1
rev: 387738a
Muon: 2.57.8
libchromiumcontent: 57.0.2987.133
V8: 5.7.492.71
Node.js: 7.4.0
Update Channel: dev
os.platform: win32
os.release: 6.1.7601
os.arch: x64

• Steps to reproduce:

  1. Added OneTab using instructions outlined here -- https://blog.brave.com/loading-chrome-extensions-in-brave/
  2. Icon shows up next to the Brave icon in topmost toolbar.
  3. OneTab icon does not register any clicks at all.

• Actual result: Extension doesn't work because it doesn't register any mouse clicks.

• Expected result: Extension would work.

• 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

[jonathansampson]

Closing in favor of #9828