Note: There are several lazy loaded images bugs T207929, T199351, T209183. We'll probably want to fix these 3 bugs together.
When lazy loading imagemaps lazy loader doesn't set usemap attribute, hence breaking image maps.
How to reproduce:
Go to some article that use imagemap (the image shouldn't be small image, and not in the first section - lazy loading is done only for large images) and compare the desktop and the mobile versions.
Example:
{F27201849} [[ | URL ]]
== Acceptance criteria
[] The `usemap` attribute is copied across as data-usemap in the placeholder
[] The `usemap` attribute is copied across when JS loads the image
= QA steps
Visit https://en.m.wikipedia.beta.wmflabs.org/wiki/Image_Map_test
Click the are of the image that's Australia
Expected: Can navigate to Australia page like on desktop.