Remove <video> width and height attributes from intrisic size logic

The width/height content attributes already influence specified style
via HTMLVideoElement::collectStyleForPresentationAttribute, to also
influence the intrinsic size has never been part of the spec:
http://whatwg.org/html#the-video-element

The test case passes in Firefox Nightly and IE11 Release Preview,
but fails in Opera Presto, which has no default intrinsic size.
Opera is actually correct per spec, but fixing Blink can be done
in a separate bug.

BUG=310122

Review URL: https://codereview.chromium.org/38313002

git-svn-id: svn://svn.chromium.org/blink/trunk@160491 bbb929c8-8fbe-4397-9dbb-9b2b20218538