
PASS HTMLElement constructor must throw a TypeError when there is no derived class 
PASS HTMLElement constructor must throw TypeError when custom element is not well defined 
PASS HTMLElement constructor must infer the tag name from the element interface 
PASS HTMLElement constructor must allow associating an element interface with multiple tag names 
PASS HTMLElement constructor must allow subclassing a custom element 
PASS HTMLElement constructor must allow subclassing an user-defined subclass of HTMLElement 

