Main Frame Window grows by 10x10 pixels upon each restart of the Editor

With each relaunch of the Editor, the Main Frame Window grows by 10x10 pixels.
The editor viewport, in turn, grows by a few pixels in response to that.

See attached three images: Window1, Window2, Window3 Each window was screen captured at 100% with Snatch-it showing a progression of 10 pixels larger in diameter each time the editor was opened.

Not a regression: Occurs in UE4.14.3

1. Open a new blank project in UE4.15
2. Resize Main Window so that it is a floating Window
3. Take a snapshot with Snag-it or similar software
4. Close the Editor making sure keep layout is selected
5. Open project again
   RESULT: The main window is now 10 pixels greater in diameter
   EXPECTED: The main window to remain the same size each time the editor is opened