Very large photos have a tiled thumbnail when uploaded

[tomsaleeba]

Env: PWA mode in Chrome 80.0 on Android 8, LG V30

Steps:

• launch app
• start new obs or edit one
• attach a new photo
• select this 108MP photo from a Samsung S20 Ultra: http://testdata.techotom.com/originals/samsung-s20-ultra-108mp-photo.jpg

Expected:
The thumbnail that's generated is a single copy of the photo.

Actual:
The thumbnail is tiled a heap of times.

The preview still renders correctly if you tap on the photo so it's not a deal breaker.
The blob image itself isn't tiled, I confirmed that by editing the page to render the blob separately:

Playing with the CSS for the thumbnail, I couldn't fix it easily so it's a problem for later.