Draft steps on CSS a11y

Rich, Cynthia, and I met with Rossen Atanassov, co chair-of the CSS 
Working Group, while at CSUN 2016 to hash out a proposal to address the 
accessibility concerns we've been identying in CSS specs. I had delayed 
sending a summary of the discussion to the WG until we had confirmed we 
all shared the same understanding. For archiving, I am sending the 
following points, which do not represent a consensus of any group but 
are a starting point for further discussion.

  * We think we should start work on a CSS Accessibility API Mappings
    spec. This would describe how CSS should be exposed to assistive
    technologies, including or especially for the moment generated
    content. Initially it may contain placeholders for other issues
    which might later migrate to other places, or continue to be
    developed within the CSS-AAM.
  * We agree a best practices / authoring practices doc to explain how
    to author CSS well for accessibility will be important.
  * There is a need for the accessibility community to provide test
    cases demonstrating situations we're concerned about so the CSS WG
    can see them in context.
  * It may be most effective to form a joint task force between APA,
    ARIA, and CSS to work on the above. We do need to check with each
    group to see if there is support for that or if we need to find a
    different home for the above work.
  * There is a need to continue work on the navigation challenges, but
    it is clear from the discussion the solution needs to involve CSS,
    HTML, SVG, and potentially ARIA. We understand this to be a longer
    term project but needs to be clearly in the plans. Initially the
    CSS-AAM might have a placeholder section for this, and the APA WG
    should take responsibility for instigating this work.

Michael