This also happened for me in 2.7.1 -- it's a bit annoying to say the least.. I make edits, go to update the file and the text box jumps. This also happens when I rollover any other button like the 'select' button next to 'select theme to edit'. Resizing the window will reset the box to the top, but any other button rollovers will cause the jump again.
Again, this is only in Chrome.