[Editor] A Black color line appears on the bottom of scene view window while resizing.

Steps to reproduce :
1. Change the scale factor of the screen to 125% or more from Window's display settings.
2. Create a new project in Unity.
3. Undock the Scene window.
4. Expand/shrink the window multiples times.

Actual Result :
A Black color line appears on the bottom of the scene window while resizing.

Expected Result:
All sides of the window has the light blue border, no black line is visible.

Occuring On:
2019.1.0a10, 2019.1.0a9

Working fine On:
2019.1.0a8, 2018.3.0b12, 2018.2.0f1

Environment:
Windows Only