Debug tiles shouldn't use non-standard HTML attributes

[Malvoz]

col, row and zoom are non-standard attributes on <div> elements. Authors may be flagged for using invalid HTML when validating their web pages that has the component embedded. Use data- attributes instead?

[Malvoz]

May also be motivated by #176.

[prushforth]

Authors may be flagged for using invalid HTML when validating their web pages that has the component embedded.

Doubtful of this; the <div>s in question are found in the shadow root, and as such are dynamic, and created by code at run time. I don't think a validator looks inside the shadow root for a <video> controls, for instance.

I'm not saying it would hurt to use data- attributes, just that I don't it's a big deal / internal concern is all.

[Malvoz]

I think this is a similar consideration to #174. If we create customattr today and an attribute with the same name is added to the web platform tomorrow they would conflict (even if in Shadow DOM). It's probably quite unlikely that these particular attributes would ever be added as global attributes (applies to <div>) to the HTML spec though.

[Malvoz]

There's a related TAG issue here: w3ctag/webcomponents-design-guidelines#2.