Dropdown not shown completely when right click/long press on newtab button

[srirambv]

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

Describe the issue you encountered:
Dropdown not shown completely when right click/long press on newtab button

Expected behavior:
Should show the context menu within the browser depending on the position of the newtab button

• Platform (Win7, 8, 10? macOS? Linux distro?):
  Windows 10 x64

• Brave Version:
  0.12.10 RC1

• Steps to reproduce:

  1. Set max tab limit to 10(default)
  2. Open 9/10 tabs to ensure new tab button is right next to the hamburger menu
  3. Long press on the new tab button/right click on the new tab button to show the context menu, most of it is hidden

• Screenshot if needed:
  

• Any related issues:
  Dropdown shown when long pressing new tab will now show "New Tab" #5704 cc: @bsclifton

[cndouglas]

+1 from #5784.

[luixxiul]

Test plan: #5854 (comment)