Focus active webview when closing downloads-bar

[michalbe]

Fixes #3219

• 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:
Webview now correctly gain focus after closing DownloadsBar (for instance up and down keys work, like on the attached gif).

[cndouglas]

Thanks @michalbe! Works for me.

[michalbe]

@liunkae thanks!

BTW, are failed CIs a normal thing in this project? Or it's just temporary?

[cndouglas]

@michalbe It is normal, unfortunately (#5389).

[bbondy]

++