Disable pre-loading of Vomnibar iframe.
Disable pre-loading of Vomnibar iframe.

Pre-loading the Vomnibar iframe seems to be causing some issues with the
dev console.  This PR disables pre-loading of the Vomnibar.

I'm going to try this out for a while.  If it doesn't seem to sluggish,
then I'll merge it.

decaffeinate-examples/vimium,poacher2k/vimium,gdh1995/vimium,smblott-github/vimium,poacher2k/vimium,gdh1995/vimium,decaffeinate-examples/vimium,philc/vimium,gdh1995/vimium,smblott-github/vimium,philc/vimium,philc/vimium,poacher2k/vimium,smblott-github/vimium,decaffeinate-examples/vimium