[whatwg] Constructors for HTML Elements

[James Graham]

There seems to be some interest in making all concrete interfaces in the 
DOM constructible (there also seems to be some interest in making 
abstract interfaces constructible, but that seems insane to me and I 
will speak no further of it).

This presents some special difficulties for HTML Elements as there is 
not generally one interface per tag (e.g. HTMLHeadingElement is used for 
h1-h6) and making all zero-argument constructors work seems like a more 
natural API than sometimes having to say 'new HTMLDivElement()' and 
sometimes having to say 'new HTMLHeadingElement("h1")'. So the question 
is whether we can change this without breaking compat. The only problem 
I foresee is that adding new interfaces would change stringification. 
But I think it is possible to override that where needed.