Make arguments to Element methods non-optional

http://dom.spec.whatwg.org/#interface-element

Only touch methods defined by the above spec.

The added missing-arguments test passes in Firefox Nightly, and
Opera 12.16. IE11 Release Preview passes all except getAttribute,
removeAttribute and setAttribute, where it returns null/undefined
instead of throwing.

Taken together, this could break IE- and Chrome-only content.

BUG=325922

Review URL: https://codereview.chromium.org/98543009

git-svn-id: svn://svn.chromium.org/blink/trunk@163374 bbb929c8-8fbe-4397-9dbb-9b2b20218538