"File" field type and white images with transparent backgrounds #1103

Expected Behavior:

When uploading an image using the "file" field type, it should be visible even if the image is all-white with a transparent background. These kinds are images are very common when dealing with logos or icons.

Actual Behavior:

All-white images are not visible because the preview box has a white background:

Standard WordPress image UI elements use a checkerboard background or a light gray background:

Featured Image Example

Media Library Example