Verify the Class Hierarchy
==========================
Make sure the events inherit from the correct interfaces:
e.g., UIEvent > MouseEvent
Requires manual and automated tests
* manually create event and verify hierarchy
* WebDriver create the event and verify hierarchy
UIEvent
* load, unload, abort, error, select, resize, scroll
* Note: some event types may be dropped given that they don't appear to be UIEvents by other specs
that define them.
FocusEvent
* blur, focus, focusin, focusout
* blur and focus are handled in HTML5
* but they aren't sure if focusin/out are needed: see bug: https://www.w3.org/Bugs/Public/show_bug.cgi?id=25877
MouseEvent
* click, dblclick, mousedown, mouseenter, mouseleave, mousemove, mouseout, mouseover, mouseup
WheelEvent
* wheel
KeyboardEvent
* keydown, keyup
* need to show interaction with beforeinput and input, which are in the Editing spec
CompositionEvent
* compositionstart
* compositionupdate
* compositionend
* need to show interaction with the keyboard events: keydown, keyup
