Add ontoggle to GlobalEventHandlers and HTML attributes

Add ontoggle to GlobalEventHandlers and HTML attributes, as per the
specification:
http://www.whatwg.org/specs/web-apps/current-work/#globaleventhandlers

R=arv@chromium.org,tkent@chromium.org
BUG=366105
TEST=fast/html/details-open-toggle-event.html
TEST=fast/dom/global-event-handlers.html

Review URL: https://codereview.chromium.org/252373002

git-svn-id: svn://svn.chromium.org/blink/trunk@172436 bbb929c8-8fbe-4397-9dbb-9b2b20218538