Initial tooltip implementation for toolbar example

Here is an initial implementation of a tooltip behavior for the bold, italic, underline and text alignment buttons:
https://raw.githack.com/w3c/aria-practices/issue986-toolbar-button-tooltips/examples/toolbar/toolbar.html

This example makes the tooltip role a child of the button, to make it easier to position the tooltip using CSS.
The tooltip can than also be used to label the button without the use of the aria-labelledby attribute suggested last week.
Does this make sense, or should we be using aria-labelledby?

Hopefully can discuss on the call today.

Jon

Jon Gunderson, Ph.D., CPWA
Coordinator of Accessible IT Group
University of Illinois at Urbana/Champaign
1207 S. Oak Street
Champaign, IL 61820

www: https://go.illinois.edu/jongund