Description for Session Tab on Hover

[eljuno]

Test plan

#10691 (comment)

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• Did you search for similar issues before submitting this one?
  No.

• Describe the issue you encountered:
  Description tooltip when hovering on session tab have tofu and description not show properly.
  See screenshot and record for better explanation.

• Platform (Win7, 8, 10? macOS? Linux distro?):
  Win 8.1

• Brave Version (revision SHA):
  0.18.14 (ad92d02)

• Steps to reproduce:

  1. Set to 20 tab per tab set on about:preferences#tabs
  2. Create session tab,
  3. Hover to "person icon"

• Actual result:
  See screenshot

• Expected result:
  description show correctly like this one (from clicking lock icon on URL bar)
  

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

• Is this an issue in the currently released version?

• Can this issue be consistently reproduced?

• Extra QA steps:
  1.
  2.
  3.

• Screenshot if needed:
  

• Any related issues:

[cndouglas]

Looks like the variable partitionNumber is not being substituted properly either.

Also, that tooltip is not shown unless the tabs are small enough to hide the close button. Might be a usability problem.

[cezaraugusto]

setting to sprint/1 and tagging for 0.20.x as this will be fixed by #10691 cc @zentagonist