You can do it on Chrome on a tablet, but not on a phone. On a tablet, you can actually see the tabs. Long-press on the tab you want to move, then drag it to the new position. The phone's Chrome interface doesn't show you actual tabs--instead, if you tap on the multi-window icon at the upper right, you'll see all of your open Chrome windows in a stacked-card fashion, without any way of rearranging them.