White screen while loading new image during zoom in Firefox

[cdrini]

Description

When loading a higher resolution image during zooming, firefox displays a big ol' white screen while the image loads in. Should instead display the new image over the old, lower res image. However the events we listen to, ie onloaded, fire at the wrong time, and the background is white not transparent, so we can't have an image underneath. Maybe we can do something with blend modes? Or maybe this is a bug to open in FF, that the bg should be transparent?

https://user-images.githubusercontent.com/6251786/134944902-26b0462d-ac41-4e1b-aa80-64bf819b85c4.mp4

What problem are we solving? What does the experience look like today? What are the symptoms? How can one reproduce the problem?

Evidence / Screenshot (if possible)

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Expectation

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Context

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Proposal & Constraints

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