App tooltip shows up over wrong icon in Plank

[d-d-2]

Description of the bug:

Moving the cursor left and right sometimes makes the app name show up over the incorrect spot on the dock. (See attached image).

Steps to reproduce:

Move your cursor left (or right, whichever), at a constant speed (not speeding up/slowing down, just a steady motion) over Plank. If the issue doesn't reproduce, try using a slower speed. If it's not happening and you're going quite slow, try a faster speed. It should be between 0.1 and 0.6 seconds from icon to icon.

Note about low-end machines:

I am on a netbook, with some amount of graphical lag under Pantheon Desktop. (Dell Inspiron 1010). That might make it easier for me to reproduce this bug, or it might mean my mouse has to move slower to reproduce the bug than yours would. In any case, I expect this applies on all systems. I'm not sure if it applies on Plank outside of Pantheon/elementary OS, because I've never tested it anywhere else.