Allow UrlValuedAttribute:image on elements with children

[ypmict]

Hi,
I opened a new issue that is related by issue #1297
That is by using the syntax :

ModPagespeedUrlValuedAttribute li data-thumb image

the image ended up duplicate in the html just like what Mr. @oschaaf said in the original issue post

Thank you very much

[jeffkaufman]

Reproduced. If you configure a site to be:

<li data-thumb="a.jpg">
  <img src="a.jpg">
</li>

And you set in your config:

ModPagespeedUrlValuedAttribute li data-thumb image

Chrome gets:

<li data-thumb="a.jpg.pagespeed.ce.O58zxI4ffb.jpg">
<img src="xa.jpg.pagespeed.ic.hq49LFhoZa.webp">
</li>

That is, <li data-thumb=...> just gets cache-extended, while <img src=...> gets fully optimized. On the other hand, if you have:

<li data-thumb="a.jpg"></li>
<img src="a.jpg">

Then you get the expected:

<li data-thumb="xa.jpg.pagespeed.ic.hq49LFhoZa.webp"></li>
<img src="xa.jpg.pagespeed.ic.hq49LFhoZa.webp">

Going from memory, the problem is that any tag that has children isn't considered an acceptable target for image optimization, so it only gets cache-extension here. I'm not sure why we have this limitation, but it should be fixable.

I've added this to the Work Prioritization sheet.