Shows notification caret on pinned tabs

[jonathansampson]

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).

Resolves #8626

Test Plan:

1. Open a new tab and navigate to google.com
2. Pin the tab
3. Confirm presence of caret when Google requests location

[cezaraugusto]

++ thanks!

[cezaraugusto]

btw moving to 0.15.400 to match issue milestone pls change if this should ship in .300