The syntax for implementing a SkyElement is now:
<sky-element name="element-name">
<template>
<!-- template here -->
</template>
<script>
module.exports = class extends SkyElement {
attached() {
// ...
}
// .. methods here ..
}.register();
</script>
</sky-element>
The register() static method on SkyElement subclasses calls
document.registerElement() and returns the generated constructor.
It uses the parent <sky-element>'s name attribute to set the name
of the element.
R=rafaelw@chromium.org
Review URL: https://codereview.chromium.org/788943003
