Blue line briefly flickers when moving mouse in Sprite Editor "Edit Outline" mode, OSX Metal only

1. Create any project in 2D on OSX
2. File > Build Settings > PC, Mac & Linux Standalone > Player Settings > Enable "Metal Editor Support Experimental"
3. Import any sprite
4. Click on the sprite and open "Sprite Editor" from Inspector
5. Change mode from "Sprite Editor" to "Edit Outline"
6. Move the mouse along the outlines of the sprite, and in and out of the sprite

Expected: There should not be flickering.
Observed: There is a blue line that flickers intermittently as the mouse is moved.

Occurring on: 5.6.0f1 onwards until 2017.1.0b2 (current latest)