EventHandler IDL attributes should be enumerable

EventHandler IDL attributes should be enumerable
https://bugs.webkit.org/show_bug.cgi?id=153595

Reviewed by Sam Weinig.

LayoutTests/imported/w3c:

Rebaseline W3C HTML test now that EventHandler attributes are enumerable,
as per the specification.

* web-platform-tests/html/dom/interfaces-expected.txt:

Source/WebCore:

Most of our EventHandler IDL attributes were marked as [NotEnumerable]
but should not have been according to the specification:
- https://html.spec.whatwg.org/#globaleventhandlers
- https://html.spec.whatwg.org/#windoweventhandlers

Firefox and Chrome behave according to the specification.
This patch aligns our behavior.

No new tests, already covered by existing tests.

* dom/Document.idl:
* dom/GlobalEventHandlers.idl:
* page/WindowEventHandlers.idl:

LayoutTests:

Rebaseline test now that more EventHandler attributes are enumerable.

* js/dom/dom-static-property-for-in-iteration-expected.txt:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@195778 268f45cc-cd09-0410-ab3c-d52691b4dbfc