edx/edx-platform — pull request #1798 by polesye (2013-11-27 11:39:53+00:00)
Title: BLD-533: Improve calculator's tooltip accessibility.

Add possibility to navigate through the hints via arrow keys.

**Keyboard Support**:
If focus is on the hint button:
* Enter: Open or close hint popup. Select last focused hint item if opening.
* Space: Open or close hint popup. Select last focused hint item if opening.

If focus is on a hint item:
* Left arrow: Select previous hint item.
* Up arrow: Select previous hint item.
* Right arrow: Select next hint item.
* Down arrow: Select next hint item.

**Goal** ([composite](http://www.w3.org/WAI/PF/aria/roles#composite)):
>Authors SHOULD ensure that a composite widget exist as a single navigation stop within the larger navigation system of the web page. Once the composite widget has focus, authors SHOULD provide a separate navigation mechanism for users to navigate to elements that are descendants or owned children of the composite element.

Related links:
- [Menubar: ARIA](http://oaa-accessibility.org/example/26/)
- [aria-activedescendant](http://www.w3.org/WAI/PF/aria/states_and_properties#aria-activedescendant)
- [composite](http://www.w3.org/WAI/PF/aria/roles#composite)

@jmclaus , @auraz , @frrrances please review.