Rendering Offscreen Using Non-Fullscreen View Creates Black Border

Issue has been observed in 4.19.1 from EGL and Main CL 4027311.

Per licensee:

We recently switched from UE 4.18 to 4.19, and noticed several issues when doing offscreen rendering. To illustrate them, I managed to recreate a minimal offscreen rendering class with the same scenario in both versions of the engine. Both projects are attached here : 4.18 and 4.19

 It would helpful to know if there is a way to get the 4.18 behaviour in 4.19 by modifying the source code of the attached example.

1. Open both attached sample projects
2. PIE
3. Observe that in 4.19 version, Cube has black border, whereas 4.18 version has color of the canvas background (yellow in this example).

Expected: 4.18 and 4.19 behavior are the same