iframe omnibar: refuse all keydown events if not active
iframe omnibar: refuse all keydown events if not active

just in case that the iframe is hidden but holds focus,
    which should not occur.
The last commit 9524f7f8a5bdc9ba27f18988fa899e024b8056ab
    is just for such a case.

gdh1995/vimium-plus,gdh1995/vimium-plus,gdh1995/vimium-plus