Fix the issue that the title of unloaded tabs shift down

[luixxiul]

by specifying the height in pixel

Follow-up to #10533. The issue is a regression introduced with that PR.

Auditors:

Test Plan:

1. Open the browser
2. Load several tabs
3. Close the browser
4. Re-open it
5. Make sure the unloaded tab titles are not shifted down

I cannot find the exact STR but I have seen the issue several times already.

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.

Test Plan:

Reviewer Checklist:

Tests

• Adequate test coverage exists to prevent regressions
• Tests should be independent and work correctly when run individually or as a suite ref
• New files have MPL2 license header

[NejcZdovc]

++