Removes FocusBorder from views

This patch removes FocusBorder from View along with
View::OnPaintFocusBorder. Views that want to render focus and that
need to allow overriding get a Painter that is responsible for
rendering the focus. Views that render focus differently must override
OnFocus/OnBlur to SchedulePaint the necessary region.

This patch simplifies View and cleans things up for views that don't
ever want to paint focus, or paint focus differently (say TableView,
or Textfield). On the down side it does mean any view that is
focusable needs to override a few more additional methods. It was easy
to get this wrong previously though as a common pattern is to
override OnPaint and not invoke View::OnPaint.

BUG=none
TEST=none
R=ben@chromium.org

Review URL: https://codereview.chromium.org/105013002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238888 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238888