HtmlUsage check of HTMLUnknownElement is returning false for unknown elements

[gregwhitworth]

I have the following code in htmlUsage.js:

  // If the browser doesn't recognize the element - throw it away
    if(element instanceof HTMLUnknownElement) {
        return;
    }

This is not currently working and we need to figure out a way to make it so that we don't keep tags that aren't natively supported by the parser. Assigning to @arronei to look into this ASAP. For the time being if you could provide me with an array of specified HTML tags and we'll scope our current dataset to that until the script is updated.