ReactNativeComponent -> ReactDOMComponent

In an effort to break the DOMy parts of React away from the non-DOMy parts, I'm renaming this.
Fix isEventSupported in recent versions of jsdom.

Setting the `eventName` attribute of an element to the empty string is not
enough to cause `typeof element[eventName] === 'function'` in jsdom. The
attribute value actually has to look like a function body.
Speed Owner Access (by over 9000)

Use a valid identifier (and non-string) to reduce chance of de-optimizing in V8 and Nitro.