Rename FullscreenElementStack::requestFullScreenForElement to requestFullscreen

It's unambigious without the suffix, and now matches the spec:
http://fullscreen.spec.whatwg.org/#dom-element-requestfullscreen

If there ever was any disambiguity about document fullscreen vs.
element fullscreen, there isn't any longer, at least not here.

BUG=383813

Review URL: https://codereview.chromium.org/444033003

git-svn-id: svn://svn.chromium.org/blink/trunk@179787 bbb929c8-8fbe-4397-9dbb-9b2b20218538
4 files changed