Editor window changes size each time the same project is opened

The editor window is slightly bigger each time you open the same project. This doesn't persist over to any other project. I also checked in 4.8 from p4, this also occurs in: 4.8 /UE4/Promoted-CL-2498147

1. Open a project
2. Set the Editor to Window Mode, not maximized full screen
3. Pull the Editor to the left of your screen, until it meets the edge
4. Take note of the position of the editor
5. Close and reopen the Editor
6. Realign the left side and observe the slight change in size horizontally