don't toggle the gbar when typing in new reply/compose divs

Hello! I don't know if this is where to submit changes or not (or if editing data.js is the best way), but here's a short pull request.

It used to be that hitting '/' to toggle the gbar was ignored if in an input/textarea, but the new Gmail compose and reply widgets are divs. I fixed this by checking for their "contenteditable" attribute. I tried this fix in my own settings and it works perfectly, you can toggle the gbar normally, but it isn't toggled when just typing a '/' in the reply/compose widgets anymore.