We don't need a lot of the Widget API. I also removed the
visibility code which seems to have been broken when we
removed FrameView::show and hide(), which looks like it
would have broken image loading. Unfortuantely we don't
have pixel tests or tests that load images so I can't
test this yet. Even so it's a good simplificatin since
our system has no concept of hidden widgets.
R=abarth@chromium.org, ojan@chromium.org
Review URL: https://codereview.chromium.org/691453002
FrameView doesn't really need to know about the child widgets,
which are just Scrollbars now.
I also deleted some dead code from Widget and removed FrameWidget
since we don't need that abstraction now.
R=ojan@chromium.org
Review URL: https://codereview.chromium.org/685593005