Viewport doesn't regain focus after using Find

[gulkily]

Did you search for similar issues before submitting this one?
Yes

Describe the issue you encountered:
After I use the Find (Cmd-F) feature, focus is not returned to the viewport until I click on it. This means that in-page shortcut keys (e.g. Gmail) do not work.

Expected behavior:
After I close the Find dialog (small thing in the top right corner) the focus should be returned to the viewport.

• Platform (Win7, 8, 10? macOS? Linux distro?): macOS
• Brave Version: 0.11.5
• Steps to reproduce:
  1. Open a scrollable page.
  2. Verify that you can scroll the page (press up/down arrow keys)
  3. Press Cmd-F; Type in some text into the dialog.
  4. Press Esc or close the Find dialog with the X button.
  5. Press the up/down arrow keys again. Page doesn't scroll at this point.
  6. Click on the page.
  7. Press the up/down arrow keys again. Page scrolls now.
• Any related issues:
  Viewport doesn't regain focus after closing downloads-bar #3219, Improved UI/UX of find bar #3315