Wrong border when using a ContextMenu on fractional resolution displays

[jpobst]

Creating an empty ContextMenu using the following code:

var context_menu = new ContextMenu ();
var context_button = Controls.Add (new Button { Left = 10, Top = 250, Width = 250, Text = "Right click for context menu", ContextMenu = context_menu });

produces the correct border for the ContextMenu when resolution scaling is a multiple of 100%.

Screenshot at 100%:

Screenshot at 200%:

However, when resolution scaling is fractional, the right and bottom edges of the ContextMenu border are inset 1 pixel, causing there to be blank space between the ContextMenu and its drop shadow.

Screenshot at 150%:

There should not be the 1 pixel inset border at fractional resolution scaling.