Differences in Post Process FX between Minimized and Maximized Viewport

When scaling the viewport window using the Maximize/Minimize viewport option, the post processing effects applied to the screen do not scale properly.

This issue seemed trivial at first, as the user reported the problem using Vignette, which was hard to see the difference. Upon further investigation, I tried other settings as well, and it seems to affect other Post Processing functions as well.

Regression

I tested the same issue in the binary release of 4.10.4, and the issue did not appear there.

1. Open a new or existing project with a Post Process Volume added to the scene.
2. Set the 'Fringe Intensity' and 'Vignette Intensity' within the 'Scene Color' dropdown within the Post Process Volume to the max values.
3. Be sure you can see the effects by adding geometry to the scene and focusing the camera on the object(s).
4. Click the Maximize or Restore Viewport button in the top right corner of the viewport window.

Outcome When the viewport is minimized to the quadrant layout, the post processing effects do not render the same as on maximized.

Expected The post processing effects scale with the window size.

Post Process Scale Issues Switching Fullscreen/Windowed