ScrollableArea only has one subclass now. Make all it's virtual
methods be pure virtual and delete any methods that
RenderLayerScrollableArea overrides.
Eventually we should probably merge the two classes into one,
but ScrollableArea is in platform and RenderLayerScrollableArea
is in core/rendering, so it's non-trivial figuring out what the
end result should look like. Hopefully it will become more clear
as we delete more of the scrolling code.
R=abarth@chromium.org
Review URL: https://codereview.chromium.org/711483003
We never paint scroll corners. The only thing we need them
for is so that the vertical and horizontal scrollbars don't
overlap each other. So, that's the only place left that
still computes a scroll corner rect.
We don't support resizers. Remove the code for them as well
as the CSS resize property.
R=abarth@chromium.org
Review URL: https://codereview.chromium.org/689283003
