Fix urlbar suggestions showing up when non-printable keys are pressed

[diracdeltas]

Fix #8896

Test Plan:

1. npm run test -- --grep='press keyboard shortcut' should pass
2. go to a site with autocomplete entries; ex: twitter.com. press cmd+L to focus the urlbar and the cmd+C to copy. the autosuggest dialog should not appear.

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).

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

[luixxiul]

The test plan works.