Broken off of bug 21000. Now that scrolling to reveal the highlightd node is gone, we should show an arrow pointing in its general direction when the highlighted node is off-screen.
Alternatively we could provide a way to scroll to the highlighted node in the viewport(e.g. by clicking a node in the DOM tree with Cmd or other modifier). Would it make sense?
The tooltip arrow location now denotes the general direction where the node resides offscreen (as of bug 37768 fix).