ACTION-1684: CSS-UI Review

http://www.w3.org/tr/2015/cr-css-ui-3-20150707/

Overall, I didn't see anything to be worried about, and some things look useful and interesting.

Additional comments:

3.1 box sizing.
Goal is to replace layout tables, and actually offer the same functionality. It looks like it might work. That would be a good thing.

4 outlines
Scenario given in the spec is for drawing focus 'rectangles'/ (which can be non-rectangular in the spec) without impacting layout.  Also a useful feature.

5 resizing and overflow
Some good ideas on how to handle ellipses on overflow content.
<string> can used for custom strings in place of ellipses, which is also an interesting idea. It is at risk.
Idea: I'd love to see a way to keep the content in the accessibility API and/or DOM for AT, even if it is visually clipped or ellipsed.

6.1 Pointing devices and cursors
Cursor:none seems like a bad idea. What is the use case for this?
Zoom-in / zoom-out cursors look useful.

6.3 keyboard control
Nav-up, nav-down, nav-left, nav-right can point to an element, a frame or auto. They support arrow-key navigation. This looks useful.

Ime-mode is obsolete.  Is this a concern for us?