How do you do that when the other tab is buried under three other browser windows in another space? Possible, but this makes things a lot easier. Then again, maybe the way I leave tons of stuff open across lots of spaces is just the sort of workflow that something like this is meant for...

I guess I must not have that many browser windows scattered around the place when I'm using OS X or Windows and on linux I use a tiling window manager, so its trivial to tile both windows side-by-side and then drag between them.

That works on Chrome but not Safari.

Firefox too. I did not know it doesn't work in Safari though.