Show Flash notification bar if page loads small/hidden Flash elements

[diracdeltas]

Fix #7523

Test Plan:

1. automated flash tests should pass
2. go to a site that has an invisible Flash object. If Flash is globally enabled, it should show the notification bar. @srirambv or @alexwykoff may have an example of such a site.

• 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).

[bbondy]

++ thanks

[srirambv]

Can use www.wordtimebuddy.com which has a small flash element

[diracdeltas]

actually https://www.worldtimebuddy.com/'s flash element is greater than 20px so it doesn't trigger the notification bar. reverso.net is a good example once #7752 is merged.