Several things needs to be fixed:

1) Qt icon

The icon is referred to as: 
:/data/qticon64.png
it needs to be:
qrc:/data/qticon64.png

Otherwise chromium will rewrite the url.

2) Firefox
We need to use QWasmAnimationFrameHandler::requestAnimationFrame,
when writing to the clipboard
 
3) image/png vs text/html
We can choose to propagate image/png to text/html and vice versa. Or this can be
done at the calling layer.