Re: [CSSOM-view] Support centering an element when scrolling into view.

Don't forget to specify what happens when the element is too big to fit in
the viewport.

Also, don't forget to specify exactly what the area that is scrolled into
view is. Currently CSSOM View refers to "the border box of the element",
which is of course ill-defined since there can be zero or more border-boxes
for the element.

Rob
-- 
“You have heard that it was said, ‘Love your neighbor and hate your enemy.’
But I tell you, love your enemies and pray for those who persecute you,
that you may be children of your Father in heaven. ... If you love those
who love you, what reward will you get? Are not even the tax collectors
doing that? And if you greet only your own people, what are you doing more
than others?" [Matthew 5:43-47]