From: Ryosuke Niwa [mailto:rn...@apple.com]
> As we have repeatedly stated elsewhere in the mailing list, we support option > 1 since authors and frameworks can trivially implement 2 or choose to set > "prototype" without us baking the feature into the platform. At first I was sympathetic toward option 1, but then I realized that with ES6 modules all script loading becomes async, so it would be literally impossible to use custom elements in a .html file (unless your strategy was to wait for element registration, XHR the .html file into a string, then do `document.documentElement.innerHTML = theBigString`). In other words, in an ES6 modules world, all custom elements are upgraded elements.
